I've compiled a list of pairings that are either directly stated in the game itself, greatly hinted at or plausible based on evidence. This isn't a list of all possible combinations of characters, just something to talk about the ones that are plausible. I start with ones that actually exist, and work my way down to the ones that are possible on evidence.
Just because they're old, doesn't mean they're tired of each other. In fact, Doug and Ileyda are extremely close and supportive of their partner, willing to stand together in the face of danger. Doug is also ready to do anything to protect his wife...even if it kills him!
Their past is a driving force behind a lot of Doug's actions in-game. Twenty years ago, their only daughter, Elizabeth, was killed by Falcken during CIMA's attempts to seek out the Plug and open the Singularity. Though little is known about the details, what we do know is that the Gate Guardians failed to protect her, causing Doug to take out his anger on them and mistrust anyone in the organization. Iledya does seem to bear a little mistrust as well, evident by her 100 Trust conversation with Ark, however instead of acting on it, she tries her best to make Ark understand why Doug is the way he is and begs the youth to not be offended by his mannerisms.
You don't see much more about them in the early game, because Doug is found fourth while Ileyda is found eleventh. However, on the second floor of Lonely Factory, he hears her voice even though she isn't anywhere around. Walking off in the direction, he is caught in a Teleport Trap. Still, Doug shrugs it off as CIMA's usual tricks, his mind solely on finding his wife. When he does, he fights his way to her with all his strength, and they reunite, where he tells her that he couldn't go on without her. Suddenly, Falcken appears, and Doug begs Ileyda to run and save herself. However, she isn't going to desert the man she loves, also not wishing to live without him, and they prepare for battle...
Though we don't see the fight itself, our view returning to Ark before it starts, we do arrive to see the moment Doug falls. However, Falcken retreats upon seeing party crashers, and Ileyda begs for Eberle's help. But Falcken perceived that, setting a trap to spring the moment Ark, Ivy and Eberle were in the room with the couple. The Gate Guardians are able to destroy the CIMA attacking and Eberle successfully saves Doug's life. Both are grateful to be together again, and even moreso when Ark is able to slay Falcken and avenge their daughter.
For the rest of the game, Ileyda remarks about how much Doug is changing for the better, even finding it in his heart to trust Ark despite his lingering anger at the Gate Guardians in general. She thanks Ark for all he'd done for her husband and how he seems to be happy once again.
They, along with Philis and Telmia, form the second team to infiltrate Night Trap, where Ileyda tells him that it won't be his fault if they die. True to his usual spirit, Doug insists that no one younger than him dies, including Ileyda, even sending her away when he fights Frawdia by telling her that if he falls then she needs to look after Philis. She also shows that her priorities are similar to his in protecting the younger ones, insisting that if it came down to it Doug should protect Philis before her. However, they make it through together, and are able to find a new life on the frontier thanks to Ark and Ivy.
Verdict: There are plenty of sweet moments between the pair, and lots of mutual support. It shows that no matter how old you grow, your love for one another doesn't have to grow old too.
Children: Their only child was Elizabeth, but she died twenty years earlier. Most likely, she was around sixteen since Doug's line about her being Philis' age if she'd lived makes no sense considering Philis isn't even twenty yet. It was most likely supposed to read that she was Philis' age when she died; it's not like Natsume isn't already known for gaffes in their scripts.
Like with Doug and Ileyda, these two were married before the story begins. However, the difference is that they are a much younger couple, having two little children rather than one who would have been in her thirties had she lived. But they are equally devoted to one another and to their kids.
Not a whole lot of their past or pre-game motivations are mentioned. We do know that Jean is the one who taught Eberle first aid, as mentioned when he compliments her on saving Telmia's life. Other than that, their backstory is simply that of a family going west in search of a new life.
Early on, they are both confident in their chances. After all, they have one of the Six Stars there to protect them, and both seem to trust Jester's statement about Ark and Ivy showing promise. Even after the Gate envelops the train, they are more concerned for Ark, Ivy and their children than worried about what could happen with CIMA. And after everyone loses Trust for the duo, Eberle, Jean and their children don't make as much of a fuss as some other characters in the game *glares at Vanrose and Doug*.
When the group gets separated, Eberle is the fifth person you find while Jean is technically the twelfth and actually the thirteenth. So, like with Doug and Ileyda, there isn't a lot of interaction between them in the early game. Still, in between her concern for the children and wishing for the others' safety, Eberle finds time to think about Jean. But since he isn't there, Eberle does her best to use her medical knowledge to protect the others, even saving Doug's life when he's downed by Falcken trying to protect Ileyda.
Eventually, on the third floor of Twilight World, they come across Jean stranded on the other side of a column...a broken bridge blocking the way to the necessary pressure plate! The children volunteer to rescue their father, while all Eberle can do is watch, hoping that nothing happens to any of her family. In the end, the rescue is successful and the family shares a heartfelt reunion at the exit to the floor, complete with hugs. Though their dynamic is more the family as a whole than just a couple's reunion, it shows how close all four members are. Eberle seems relieved to have her husband back...but that's when things get shot to hell again.
Jean convinces Ark to rest the night, and wakes his family up once he's sure the others aren't going to overhear. He tells them that he's found a way out, but only four people can be saved. Though nobody clearly wants to desert the others, he eventually convinces them with the need to warn people about what happened since Ark isn't likely to beat Pike Nighttrap. They are still uneasy about the ethics, but the rest of his family follows him into Phantom Snow on Trust alone.
On the third floor, however, they discover Telmia, injured. Halley wants his parents to save her, but Jean isn't willing to budge since only four can use the route he found. However, by refusing to treat an injured person, and Halley's resulting rant on how that's not how his father is, they begin to doubt it's really him, just before "Jean" transforms into Genox. The CIMA remarks about finding what he wanted, and teleports away. Eberle does her best to heal the injured woman, but she is unable to do as good a job as Jean would have. However, luck is on their side, as Telmia insists that Jean is on the floor below them.
With Halley leading the way, the group at last comes upon the real Jean. Like before, they need to operate a pressure plate over a broken bridge, and this time they're up against a time limit as Telmia collapses again. Halley clears the way to the plate and Emmy stands on it while he goes and gets his father to safety. The family reunites at the entrance, where the adults work together to save Telmia. Though Jean insists that Eberle did a good job, her first aid got Telmia far enough so he could treat her, she is humble about it, saying that he was the one to teach her after all. They decide to wait for Ark, just so Telmia can rest.
Eberle can't believe she mistook an impostor for her husband, however the joy of being together again far overshadows this. Once more, she and her family are confident since they are no longer apart. Though they don't have a conversation in Night Trap like the other couples, Jean is constantly rewarded with the encouragement of all three members of his family. He trusts Eberle to take care of the children while he fights Fallaysa, and all four share a laugh after he asks if he's as strong as Ark. They also call out to Halley and Emmy, begging the two not to sacrifice themselves, and most likely worked together to save Ivy after she was wounded fighting Pike.
Verdict: There are some cute moments between them, however this pairing was probably intended more to show the mutual support between all members of a family.
Children: Halley (10) and Emmy (8). Halley looks like his father while Emmy looks like her mother, and both are important to the game's storyline.
Everybody's favorite dysfunctional relationship! While they are engaged to each other, Diana has become frustrated with Rick's cowardice and tendency to run away from things that are too hard or scary. She debates whether coming out to the frontier with her fiancé and their two best friends was a good idea, and is one of the most angry pioneers to find out they've been trapped in the Gate World. However, despite the rocky start they get off to in-game, everything works out well in the end.
At first, Rick is excited about the future that awaits him on the frontier, while Diana is having second thoughts about leaving the city. But when things start to go wrong, Rick immediately enters panic mode and Diana harps on her decision landing her in CIMA's hands. This is probably the only instance of a backbone Rick ever shows in relation to her anger, as he reminds Diana that she wanted to build a new life on the frontier with him. He tells her that since she's his fiancée, she has to stick with him but she counters with the fact that as a man he should be protecting her. We don't get to see much more of this little lover's quarrel, because Diana promptly shoos Ark and Ivy away to go do something about the situation. But it does stop by the time they go into the Gate, as Rick has the panic attack to end all panic attacks during the transfer! All Diana can tell him is to shut up and grab something.
Rick's nervousness and Diana's frustration are evident inside Beginning World, as she blames him for the disaster and he tries to be brave...sort of. In the end, however, the group is split up and you won't see either of them for another nine dungeons. So most of their story was pushed towards the end.
It's evident from the start of finding Rick that he's not only scared of CIMA, but worried about Diana and what she thinks about him. He's nervous that she doesn't love him any more because of his antics, while Yurald insists that if he hold his head high she will notice. Rick vows to try and be brave, but still finds it hard to do. However, he will try...for Diana's sake.
When they find Diana in Air Garden, she insists that Rick not come because it's a trap. He doesn't care, more worried about her than himself, and ends up getting both of them and Vanrose tossed down a hole. Diana decides to put the blame all on Rick, and latch onto Vanrose in an attempt to make him try and be brave (it's seemingly a variation on Operation Jealousy, except she's trying to get him to be braver rather than admit his feelings). Sure he tries...it's just that he's not ready yet and just standing on a switch near CIMA makes him run away in terror. Angered at his unreliability, she promptly tosses her engagement ring at his face, then starts flirting with Ark and Vanrose, both whom try to ignore her the best they can while Shelley takes their side in hopes of getting her to quiet down.
Despite her insistence to the contrary, Shelley and Philis seem to realize that Diana is simply pulling a huge stunt in order to get Rick to act brave. Things aren't as easy for that plan as the woman hoped, though, as Vanrose is, in her words, "stuck on Shelley." Plus, Ark is right in his insistence that he's too young for her. But unbeknownst to Diana, she'll get her chance to see Rick in action sooner than she thinks.
Two dungeons after she breaks up with him in a rage, a Teleport Trap laced treasure box separates her and Rick from the others. He immediately asks if she's okay, and tells her it was probably the chest. Diana thinks it was dirty, but knows they can't stay there forever. When Rick asks what to do, she tells him that she's counting on him as they move on. He's surprised, but Diana reminds him of the fact that he's the only other one there and she can't lead. Immediately, she begins telling him what Vanrose would do, and he asks why she doesn't just marry him if she likes him that much. Diana responds, asking if Rick is running away from her now, telling him that he ran away when he didn't succeed in the city. Rick finally understands what's up with her anger, and agrees to not run away again. Giving him one last chance, Diana begins to follow him through the level, stopping to wait for the others when they arrive at a dead end.
Like the last one, there is a long bridge and two pressure plates: one on their side and one on the other. But this time, there is no Vanrose to step in if Rick gets scared; it's all up to him to get Ark over the bridge to them. With little reservation in his voice, he asks Ark to allow him to be in control until the latter gets over the bridge. Also, he asks Vanrose to protect Diana if something should happen to him, ignoring the latter's protests as he moves for the switch and telling Ivy that he can stand firm till Ark gets over the bridge. Diana quickly notices this, begging him not to die and threatening to leave him if he does. Eventually, Ark arrives at the other side to take control again and brings everyone to safety.
At the exit, Diana chews Rick out for thinking that she'd be happier with Vanrose, insisting that it's Rick she couldn't live without. He vows to be brave from now on, and she accepts her engagement ring back. Their relationship renewed, the group heads down to face Sawma on the lower levels...though Diana is thoroughly embarrassed about having told Rick her true feelings. He's happy to have resisted the urge to run away, and the fact that Diana truly loves him, and doesn't do anything cowardly for the rest of the game.
In Night Trap, Diana says that the dungeons were good for something if they got Rick to become braver, and mentions how much she believes in him. In turn, he tells her that he can do anything if he's with her, and that they can be brave together. Like with Doug and Ileyda, they have a conversation when they set off through the fourth teleporter, however when Rick starts to get emotional Diana yells at him not to get mushy. Though something tells me, knowing her personality, she was probably more embarrassed than anything else. Something also tells me that her response of "don't panic" to his nerves upon encountering Pike was more a suggestion in the form of sarcasm, rather than outright trying to calm him down. But without voice acting, I have no proof as to either claim.
Verdict: Dysfunctional as hell, but still cute at times. They're in for an interesting future together...that's for sure.
Children: Not yet, seeing as they are only just engaged. But considering Rick's 100 Trust Conversation has him planning to name his son after Ark, I'll say that will be the name of their first male child. In my fanfics, they do have a son named Ark (nicknamed A.J. to avoid confusion...though that makes his name very awkward due to the last initial system), who looks like his father and has his mother's eyes. Meanwhile, his twin sister, Lilly, looks more like her mother with her father's eyes. Both were born four years after the game, and Lilly is sort of a leader figure to the other characters' children (having Diana's strong personality). A.J. is by no means as cowardly as Rick, he's just smart enough to not fight with Lilly. Though deferring leadership to her sometimes gets him in trouble with their more macho classmates...
Unlike the previous couples, these two aren't actually hooked up at the onset of the game. Sure, they were old friends, along with Rick and Diana, but nothing has come of it by this time. However, within the game itself, their concern for one another is shown on many an occasion, and little hints are dropped here and there (i.e. being the only non-couple or family unit who appear together in the Character Books).
The first bit of evidence comes when the group is being sucked into the Gate World itself and you are treated to a montage of characters being worried about by important people in their lives. Immediately after Diana yells at Rick for his panic attack, Vanrose runs in to see if Shelley is okay, being the only person not a parent or current love interest to show concern for someone else. Shelley, being the strong woman she is, assures him that she's perfectly fine.
Skip ahead a few dungeons, till you finally locate Shelley in Strange World. Vanrose cries out when he sees her, yelling that he'll come to rescue her. In his Talk sessions on that floor, he seems worried about her despite how capable a fighter she is, and relieved once the rescue is successful. Once everyone is at the stairs, and Vanrose is expressing his distrust in Ark, it is Shelley's yelling that gets him to quiet down and stop complaining. No other character in the entire game has that kind of power over him, showing that he is more willing to listen to Shelley than anyone else.
When Vanrose decides to go the "easy" way through the dungeon, despite Ark warning it could be a trap, Doug insists on joining right away due to his own issues with Gate Guardians. Vanrose wants to know what Shelley is planning, since she seems to trust Ark more than he, and she agrees to go along to "protect" Vanrose. The way he says her name could either mean he's embarrassed, or not understanding why she said it that way, though without voice acting we can't be 100% sure of his tone. She notes that he's always been stubborn, and hopes they survive the mess once he mentions how he trusts himself more than anyone. Shelley isn't as overconfident in the situation, telling him to back up his words with action, though in no means is she as rude as Diana is when she's giving Rick a piece of her mind.
Eventually, as Ark figured, the trio runs into a trap. Vanrose's only concern is that Shelley get to safety with Doug, however she is yelling at him not to be so stubborn, to allow the others to come save him instead of sacrificing himself, and even tells him that she couldn't forgive herself if he was hurt. He demands that she get to the other side, just as worried about her as she is for him, and tells her and Doug to find the others when they do. When Ark finally arrives, Shelley begs for help in saving Vanrose. He does so, and later she tells Ark that Vanrose'll get over his feelings of embarrassment, showing how much she knows him and his moods.
Go forward once again to the next dungeon, Sky Garden. A group of Byuno appear, transporting Shelley, Halley and Yurald to another part of the dungeon. The second Vanrose notices Shelley is missing, he's instantly at Ark's throat, demanding to know where she'd gone and yelling that he wasn't a good Gate Guardian when he couldn't provide an answer. He is only stopped when Eberle realizes that Halley is missing as well, since now the others have brought the focus back to the bigger picture of finding their friends. Though he does get in one more jab after control switches from Shelley back to the main group, telling Ark that nothing better happen to her, and spends the next floor or so worrying about what he'd feel if something did go wrong. After locating the other group, he cries out in joy to find her safe, yelling at Ark to let him go to the switch so they can reconnect the bridge and save her. At the exit, he begins to get emotional and starts to tell Shelley how he'd feel if something happened to her, but manages to choke up before he gets there. She knows what he means, though, and thanks him for caring.
When Vanrose is separated from the main group with Rick and Diana, we see how much Shelley actually trusts him as well as a clear difference in their personalities. While Vanrose freaks out when she's missing, Shelley is calm, knowing that he'll pull through in the end. However, when everyone is finally together again, Diana gets mad at Rick and breaks up with him, flirting with Vanrose and Ark instead. Shelley tries to calm her down, and looks pretty angry when she suggests that she's serious about Vanrose; I haven't seen her give a short, curt sentence like that since she was berating Vanrose for his treatment of Ark. It's after the dungeon that Diana mentions Vanrose being, "stuck on Shelley"; as if his constant worrying about her wasn't enough of an indicator that she might mean more to him.
Though both of them are willing to comment on their beliefs that Rick and Diana can patch things up, and how said patching up eventually goes over, not much more is heard between them till the end of the game, due to them not being separated again. However, when they and Claude form the first group to infiltrate Night Trap, Shelley decides to ask Vanrose what they'll do if they survive the whole mess. While Vanrose wants to talk about their future once they get back to the real world, he also apologizes to Shelley for not wanting to continue the conversation at that moment. The rest of the way through, they show confidence in going together, and after the final battle both try to tell Ark not to give up and that they can save Ivy.
Verdict: I'll say once they get out, they're going to have that conversation on their futures and decide to start dating. Pretty much all the emotion's there, just not the official word on their relationship.
Children: Due to the fact that they're not yet together, they have no children, however, I gave them a son in the case of my fanfics. His name is Azel, he has his mother's hair and his father's eyes and is born six years after the game. Though the youngest of the quartet of Next Generation Gate Guardians In-Training, he's just as determined as his older friends. However, he is a bit on the short side, won't hit a growth spurt for another two or three years, and it is the cause of conflict for him at times.
Now we get into more speculation and less full story evidence. This is because there is no resolution for Ark's love life at all within the game. And as it stands, neither of the two most likely girls (Ivy or Philis) are anything more than friends to him, though since each follows a different style of classic anime/RPG pairing, they could both be likely contenders. There will be a personal opinion part at the end, since the pairings aren't set in stone and I want to show facts relating to them, play Devil's Advocate and share my opinions.
Philis is more or less the sweet, innocent character who gets along well with Ark from the start. It's hard to pin her personality type to an exact; while she does seem to be shaping up to becoming a Yamato Nadeshiko due to her nature, passiveness in regards to her feelings for Ark and ability as a cook, she doesn't fit this trope to a T due to some slight tomboyishness (i.e. going treasure hunting with the kids). She also has some qualities of the childhood friend character, and one or two moments that reminded me of Lufia II's Tia, but is not, in fact, Ark's childhood friend (unless we find out something else about them in another game). Her crush doesn't become apparent until after you rescue her in Fire Dungeon, possibly making it a Rescue Romance, even though they talk pretty comfortably before the pioneers are split up.
At the beginning of the game, Ark and Philis show that they are on friendly terms with one another as she asks him about it being his first duty and all. Possibly, Ark has talked to at least Philis and maybe every pioneer on the train before they left the station, and she was the one he hit it off with the most since they're so close in age; this is evident in the fact that she is one of the few who has a conversation at every possible opportunity on the Blue Creek and one of an even smaller number whose conversations don't include mistrust or outside arguments. In those conversations, as well as a few they have in Beginning World, he tries to assure her that it'll all be okay; he will protect her from CIMA. But they seem more friendly and less flirtatious, so whether or not she has any emotions for him at this point is more or less the call of the individual player.
Philis is the eighth pioneer rescued by Ark and Ivy, and there is a lot of interaction between them in the dungeon. At the start, it seems like she's merely frightened, and he's calming her down. But at the exit, when she mentions that she was happy to be saved by Ark, Ivy comments on how he must be happy to have a cute girl be grateful to him. Philis thanks him once again, but even as Ark is trying to say it's his job, he starts blushing which leads to Halley and Emmy making fun of him. Lucky for Ark, Eberle moves the conversation back to the fact that Philis is safe, with some help from Doug and Vanrose.
Later on, Philis falls into a crevice that suddenly opens up, and both Ark and Doug jump in after her. Neither party questions Ark why he jumped in, most likely assuming he was just doing his job as a Gate Guardian, though Ark does ask Doug why an old man like him did something so dangerous. Turns out, Philis reminds Doug a bit of his daughter, since she was the same age. However, Doug yells at him when he's trying to understand the old man's pain, and before it can escalate, Philis yells back, reminding Doug that he can't blame Ark for something that happened before he was born. With a last vow to protect them, Ark begins leading the two through the dungeon.
Soon, they come to a room filled with CIMA. Philis begs Ark not to go, worried that he'll die, but the youth insists that he'll be fine; after all, he can't protect them if he dies. Though she isn't convinced, he reminds her that he's the only one who can do it and asks Doug to take care of Philis for him. When they finally make it to the exit, she asks if he's okay and Ark responds by asking if he looks dead. She chastises him for making fun of her concern, and he apologizes. One more insistence that he's fine for Doug's sake, and Ark is ready to lead them onward.
At the boss chamber, Philis is again insisting that Ark not go forward because of her fears of him dying. Even after he insists it's the only way to find Ivy and the others, she tearfully begs him not to go until at last he moves onward, telling Doug to protect her. Since Ivy's group arrives on a secluded piece of land, Ark fights the boss battle on his own, which opens the bridge to reunite the two groups. Philis immediately begins swooning over Ark's battle prowess, but before he could comment on what he thought of it, other than making a sound that could mean embarrassment or him trying to be modest, the second group returns and Ivy once again is teasing Ark about how well he and Philis get along. When she says she's joking because she can't imagine any girl liking Ark in that way, Philis immediately respond by commenting on how handsome he is. Though Ivy is shocked to find that the other girl is serious, Ark, tells his partner to knock it off. She apologizes, and the team is off once more.
The entirety of Philis' Trust Conversations consists of her attempts to reveal her true feelings to Ark. After being too embarrassed to continue on multiple occasions, she eventually is able to admit that she likes him in their 100 Trust Conversation. Not love, like, but it was as close as she got before she once again succumbed to her nerves. Even her mother tries to help hook her and Ark up in her own 100 Trust Conversation, though Ark still doesn't get what the heck is going on.
If Philis wants to ever win in this love duel, she will most likely need to overcome her shyness around Ark. Most of their conversations throughout the game (six of eight story/Talk Session conversations that involve her worried about Ark or their predicament) end with her saying a simple "OK" with different punctuation, while two thirds of those have the "OK" in response to Ark vowing to protect either Philis or the group as a whole; those statements, mattering how you interpret them, could even be referring to his duty to protect rather than any romantic attachment to her. And after you get out of Fire Dungeon, only one more conversation between them exists in the Talk Sessions, and one more in game dialog, both of which are her showing concern and him saying he's just fine, plus one in-train talk session where she's trying to bring up something about Ivy; whether it was the fact that Ivy was complaining about him or Philis was trying to let go of her fear that Ark might like Ivy back is never told, since she decides against finishing her sentence. Though that's not to say she doesn't comment on him several times without him talking back and there are a few moments of her trying to counter Ivy when she's being critical of Ark. He doesn't even respond to her statement in her 100 Trust Conversation, and his response to Telmia's is a simple, "What?" And in the end, Ark goes back to his work as a Gate Guardian, so he probably won't be seeing Philis for awhile.
Verdict: It's clear that she likes him and he is at least kind to her, however Philis' shyness is a major hindrance at the moment. Plus, Ark himself doesn't even seem to realize she's flirting; his blushing could be related to the fact that A) Ivy and the children are teasing him, B) the fact that, as he told Shelley earlier, he's not used to being complimented and/or C) he is an eighteen-year-old boy who has a girl giving him attention. While Ark has a friendlier relationship with Philis than he has with Ivy (both of them are to blame for that), he doesn't seem to have the subconscious connection with her the way he has with his partner.
Personal Opinion: Ark protects Philis and Philis supports Ark. Kinda cute, but not my favorite. This is partly due to my extreme love of a certain combination of factors involved with pairing Ark with Ivy (see below) and partly due to the way I saw things in the game. I would be more likely to read than write this pairing, and anything I did write would be more along the line of a fairy tale romance or a parody story where the hero's love interest is similar to Philis.
Children: Since they're not paired up canonically, there are no official children for these two. Nor have I gotten around to think of one yet, just a daughter for Philis to have in the case of her marrying someone else. But if I think of one in the case of me writing these two in a fanfic, I will list him/her here.
Ivy might very well be considered Tsundere who uses the Taunt tactic towards Ark, and emphasizes the Tsun side of her emotions (aka Type A); here Dere side seems to only really be seen in the ending, as well as some scenes with Emmy, Rick and possibly some of her more positive comments about Ark. She is usually a bit cold towards Ark, insulting him and his abilities throughout much of the game, but does truly trust him in the end. Not that she fully goes over to the Dere side...she's still pretty tough until the very last scene where she tries to hide her crying from him. If anything comes out of this romance, it will most likely be in the form of Slap Slap Kiss since they spend a good deal of time putting one another down...even when giving compliments; I can see one of them admitting their love for the other in the midst of yet another argument more than when they're getting along, though Ivy's past could also lead to such an admission being part of a hurt/comfort scenario, either in a future game or a fanfic. It's not like it isn't common among couples in games/anime, and a lot of times the hero and the heroine end up together no matter how their attitude towards each other was at the start of the story.
From the beginning, the tension between them is obvious. Ark is a tad nervous about his first duty, and Ivy begins to complain about him being an amateur. The fight escalates, with the two arguing about whether Ivy being there a month longer or Ark being eight months older makes them more important, finally ending when Jester comes in to break it up. Of course, that only holds them at bay for a bit, and Jester is forced to both break them up again and apologize to Jean for their behavior. Everything settled down, he leaves them alone to further acquaint themselves with the other passengers...until the Gate appears and the trio gets ready for battle. It's interesting to note, that despite her earlier protests about being the senior member, she is quick to defer to Ark for the rest of the game, even though there are still fights.
Despite their obvious differences, Ivy does a good job of cheering Ark up after they are separated from the others. Though her tone of voice was probably a bit harsh at times, she gave him the encouragement to re-ignite the flame of hope within his heart. And she never said anything too rude, or called him an amateur who couldn't handle the stress; she knew that he was upset over the thought that he may have cost fourteen people their lives with his indecision. All she did was make sure he could move onward, because they needed to work together in order to escape the dungeons.
Skip ahead to Lost Forest, after Ivy and Vanrose are teleported. When they arrive at a dead end, Vanrose is sure they are sunk, however Ivy suggests waiting for Ark. Though she insists that he's quite new at the whole Gate Guardian thing and not that bright or skilled, she knows he's the type to make good on his promises; as long as he has Halley to protect, he will be able to use that as a means to overcome anything that challenges him. Vanrose is unable to tell if she likes him or hates him at that point. Not only that, but in the next scene Ark compliments Ivy's dependability right after saying her personality is a bit hard to handle. Though Ivy just wants Ark to hurry up and not comment about it once he finally does get to the switch, somewhat embarrassed by the mushy talk.
In Cold Snow, Vanrose runs off once again, determined to find a safer way around. When Ark asks her to care for the others while he goes to catch up with their wayward charge, she obeys without question, possibly indicating they have more Trust for each other's abilities then they let on. Later, after the rescue of Eberle, Ark's reasoning to assure Vanrose that Ivy will be there soon is that he knows she's been trained to act on her own as a Gate Guardian. This is followed up by Ivy telling Halley that Ark is fine, because she can't imagine him dying and leaving them to fend for themselves. Though they do get into an argument relating to how long it took her to arrive, they quickly are able to stop themselves for once, knowing that it's better to get moving towards the exit. Of course, after defeating Focajbe, Ivy tells him to be more sophisticated and he doesn't get what she means, but any argument is interrupted by the H family's laughter at his expense.
When they are in Strange World, Ark tells Shelley that he's not used to being complimented, while Ivy asks why he should be. After he gets angry about it, she says that he shouldn't get so defensive over her comments, which could mean one of two things. One, she likes to tease and anything she says should be taken with a grain of salt. Two, she is just brutally honest, and doesn't mean offense when she says those things. Either way, it might indicate there's more to Ivy's behavior towards Ark than meet the eye.
Though Fire Dungeon is more about Philis being flirtatious towards Ark, some of Ivy's lines could be interpreted different ways depending on how you see their relationship. When she says things like "Aren't you glad to have such a cute girl grateful?", "Am I interrupting a private conversation...?" and "You all seem to be getting along rather well..." most people will outwardly think that she's simply teasing Ark about how much Philis seems to like him; just because Ark is quite ignorant towards her flirtations, doesn't mean Ivy hasn't noticed them. However, there could be another meaning to it as well. Though it's hard to tell without voice acting to show the tone she's speaking in, Ivy could very well be somewhat angry that another girl is showing interest in Ark. Most likely, she herself doesn't realize this, but something inside of her is causing her to have emotions that she can't explain. The same can be said about her line wondering if Ark really was thinking about Diana's marriage proposal in Air Garden.
One of the biggest scenes, however, occurs at the end of the split portion of Weakling Forest. Ivy, in response to Rick's comments on her bravery, says that protecting people is the one thing they can believe Ark in, and she wants them to believe in her too. If it had just been left at that, nothing more would come of that little comment. However, Rick asks if she dislikes Ark, causing her to launch into a tirade about how she could never like a fool like that who is so full of himself, and that it's hard having him for a partner. Philis, calling her on her overly harsh talk, asks if it's true that she hates him, and Ivy quickly takes it back, saying she may like him as a friend...emphasis on the "just a friend" part.
Like with her talk in Fire Dungeon, this section has a possible double meaning. First of all, you don't really need to emphasize the part about just being friends if the other party doesn't question you about it. Second, such rants on their male counterpart is common among tough girls whose leader or sidekick (mattering which of the two is the main character) is the all around nice guy. And third, she turned around quickly from outright disliking him to perhaps wanting to be his friend. With some of these characters, their overly hostile attitude is due to their own denial. She isn't really trying to emphasize the lack of romantic attraction to whomever asks, but to herself. Either she doesn't want to be in love for some reason, or she herself doesn't understand what she's feeling. I've seen it so often, that whenever I see a scene like this, I can't help but believe the female is hiding her own emotions (even when it's not the canonical romance, it doesn't mean the girl is without her feelings).
But that's not the end of what happens in Weakling Forest. Upon arriving at the dead end, Ivy tells the others to wait for Ark, teasing Rick a bit when he wonders what'll happen if they die. However, she insists that he will come, that he always makes good on his vows to protect them despite how reckless he can be. Needless to say, since Ark follows the superstition about sneezing when someone is talking about you, the fact that he does sneeze is enough for him to grill Ivy about her comments when they beat the boss and she tells him it's cute of him to think the enemy is scared of him. It starts a bit of an argument, and Yurald has to break it up when the others arrive. Since Shelley asks Vanrose if their bickering reminds him of his younger days, it makes me wonder if the two of them were the same way when they were in their late-teens/early-twenties and eventually got over their differences...which might say a lot considering the two of them are practically a couple in all but name!
They have a few little mini comments here and there throughout the game, mostly in the form of Ivy giving Ark tutorials in aspects Jester didn't get a chance to explain, an argument or two that doesn't go anywhere due to circumstance or one liners that could be taken as frustration at something he said, however a good portion of the dialog between them is more them talking about the situation and being cordial to one another. Though the first conversation makes them out to be rivals, and they fight from time to time, it's far from the truth. In fact, they work rather well together, and most times it doesn't even take a fight to get them to do so. That might be part of the reason, along with the sudden teleportation alone, that he's a bit nervous when he is taken to Falcken's arena without Ivy, even though he has handled a boss on his own before; we can't count the fact that he does everything on his own in boss battles in-game, since story-wise she's still there with him. He was used to working alongside his partner, so it was a shock to suddenly be without her.
But things really hit a crescendo as the duo faces down the infamous Pike Nighttrap in the final dungeon. Ark's sword can't pierce his shield, and the team prevents Halley and Emmy from sacrificing themselves for the others. With no options left, Ivy informs Ark that there is a sword he can use, mystifies everyone by speaking about a Prophesied Time and finally tells Ark that she's entrusting him with her life and that he should believe in her. Suddenly, the girl begins to transform into a beautiful sword, causing everyone to realize that she's CIMA. Though there is no real evidence as to why a CIMA would desire to fight to protect humans, Ark insists that Ivy truly wanted to save everyone. Even when Vanrose is skeptical, knowing that their two races are enemies, Ark believes in her, yelling at Pike when he insists that the two races cannot trust one another. And because of the bond of Trust they share, they are able to defeat Pike at last.
The two return to the main chamber, though Ark seems to be paying little attention to the others as he watches Ivy transform back. Once he assures her that it's finally over, she tells him he wasn't half bad...before collapsing in a bloody mess on the floor. Ark immediately picks her up and begins to panic, begging her to live and Jean to help. When he's told how much danger she's actually in, Ark practically shuts down, crying out that she can't die, however Vanrose and Shelley snap him back to reality once the dungeon begins to collapse. They inform the boy that they have to go so they can save her, and Jean tells him that if they get back to the surface he can give her the medical attention she needs. With renewed resolve, he carries her back to the train and they return to the real world.
Though we don't know what happened over the next fifteen days, there's a good chance that Ark continued to visit her, seeing as he's there when she finally does wake up. Ark tells her that she's safe now; CIMA aren't attacking them anymore and both Halley and Emmy's resonances have calmed down for the time being. Ivy is speaking in a much softer, more nervous tone, knowing that everyone knows what she is now. She wants to go back to HQ, though Ark assures her that everyone would want to see her, because she is afraid of scaring other people. He can't argue with that statement, so after they visit Jester's grave to say goodbye, the duo heads for the station. Though Claude also wants everyone to see them off, Ark makes no motion to help him convince Ivy otherwise, willing to accept her decision. Both Gate Guardians get on the train, and it soon leaves the station.
While they are chilling in their own private car, Ark decides to show Ivy how much she means to the others. As they pass the welcome sign to the town, he makes her look out the window...where she learns that the pioneers have named their new home after the two who rescued them. But just as she's trying to dismiss it, not wanting to get emotional over their kindness, she looks out again...only to see that everyone is waving goodbye from the other side of the fence. Ark points out that they came to see her, and both take a trip down memory lane together, thinking about their adventure. The thought of being cared about makes her begin to cry, though she insists that she isn't when Ark asks her. In the end, they think about what the next mission is going to be like, as they continue on as partners.
Much of Ivy's issues could stem from her origins, and whatever drove her to help out humans in the first place. Seeing as CIMA and humans are practically at war with one another, and the way she acted in the ending, there's a good chance she's afraid of being left all alone when others find out what she really is. With pioneers she's simply protecting, there's less of a chance in her cover being blown or forming a strong emotional bond since after she's done she goes on to her next mission. However, if Ark is her partner, she will be working with him all the time, and the chance of emotional attachment to him is much greater. That could lead to a higher chance of her cover being blown, and greater mental pain when he deserted her over it, so she might have decided to push him away with her argumentative behavior. Lucky for Ivy, though, her partner saw the truth of her desire to protect others, and has no plans of leaving her any time soon.
Though it's too early to tell based on just the ending, seeing as it could be fueled by her emotional state, who knows if their friendship and possible romance will improve now that he knows. Since he is sharing an important secret with her, something that could prove fatal if it gets out, Ark is now not only protecting his assigned pioneers but his partner as well. If indeed her teasing was partly due to her fears of being deserted by someone she cared for, she doesn't have to worry about that anymore. She might also feel safer around Ark now that he's keeping her secret alongside her.
Of course, if her teasing was the result of just being someone who liked to tease, they have a rockier road if they're going to ever make it in a relationship. Ark would have to learn not to take everything she says so seriously, because it's just her nature. And Ivy would have to learn to lay off him when he's getting offended. In this case, the relationship would take a lot more compromise and working out the kinks.
Verdict: They seem to trust each other deeply and work well together despite their complaints. However, Ivy is still a bit stubborn and Ark takes her comments a bit too seriously. Not only that, but Ark is much more cordial to Philis than he is with Ivy; not to say that Ivy doesn't share some of the blame for that. They do have an unspoken Trust between them, shown from early on in the game, however if they want to move on to a higher level of commitment, they have to learn to be as friendly towards each other in their downtime as when they are in combat. Heck, since they are both Gate Guardians who work extraordinarily well together, they could become quite the formidable Battle Couple indeed.
Personal Opinion: Truth be told, I happen to have a bias towards this pairing for several factors. One, I like the Romeo & Juliet-esq feel of two groups at war with one another and someone from each side falling in love; that love doesn't have to result in peace, though that's a nice bonus. Two, I have a soft spot for the bickering couple who shows they care in the middle of it all. Three, considering their design is a homage to the Lufia series (red-headed boy and a blue-haired girl), a possible future romance would be another nice homage. And four...everything from when Ivy transforms till the end! This is my definite pairing of choice if I'm writing CIMA fanfics.
Children: Just like with Ark and Philis, the lack of an official hookup means these two have no official kids. Though I have created two for them that I'll use in fanfiction: Misa looks like her mother with her father's eyes and is born five years after the game, while Ash looks like his father with his mother's eyes and is born eleven years after the game. Misa, along with the G twins and Azel, form a posse who are trainee Gate Guardians while Ash is best friend's with Philis' daughter. Though due to her position, the former deals with more of the issues that come from being a halfbreed than her brother...