Interaction
Kenshin and Kaoru
They're obviously in love!!! Though they're not good at expressing how they feel (Kaoru often hits Kenshin to cover how she actually feels for him, and Kenshin pretends to be indifferent/oblivious about Kaoru's love for him), anyone with eyes can see how deeply they care for each other. Though at times comical, their relationship is sweet but tastefully portrayed (not like some other anime couples who seem to be kissing each other every 5 minutes. But I do wish that K&K did kiss even once!). Their romantic scenes are very limited, which makes us rabid fans all the more eager to see them. But whenever it does happen (like that goodbye hug before the Kyoto arc... sigh...), a part of me just wants to swoon in delight while another part of me just turns green with envy (why, oh why, don't I have a Kenshin in my life?). It's just so amazing to see how good and right the whole K&K thing looks.
There has been no doubt about Kaoru's love for Kenshin right from the start but Kenshin's love for Kaoru became only apparent in the goodbye scene (I loved that scene. It was so romantic, with all the fireflies glowing around them and of course, that bone-crushing hug!), and even more so in the Jinchuu arc. I was able to see in that part of the manga just how deeply he loved Kaoru. I mean, without Kaoru, he was nothing... he was content to just sit there and rot away in his living hell. Could you see another love greater than that?
K&K's relationship is the type of relationships most of us dream of having. It's cute, it's funny, but very very sweet. It is based on friendship, mutual trust and respect, and with just the right amount of passion. Though flowery speeches are not part of their interaction, their actions more than just make up for it. Both of them are willing to sacrifice their lives for each other, which just goes to show everyone how much they love each other.
Kaoru and Sano
This interaction is more of a brother-sister thing. They're both protective of each other but I guess that's just about it. Sorry I can't say much about these two because I'm not really that interested.
Kaoru and Yahiko
These two squabble a lot. Yahiko calls Kaoru all sorts of rude names and Kaoru retaliates by constantly whacking him with her bokken. Whenever I watch the two of them together, it's almost hard to believe they're not related by blood. But underneath all the hitting and name-calling, both care deeply for each other. Both of them would do anything to keep the other safe. Oftentimes, Yahiko protects Kaoru (although it's quite obvious that Kaoru is the better fighter) because he wants to be seen as a man, and not a boy (though a boy he really is!).
Kaoru and Megumi
(This is only my opinion. Megumi fans are free to form their own!)
At first, Kaoru was a bit insecure about Megumi. Who wouldn't be? Megumi is very beautiful, older, sophisticated, a better cook, and seems more worldly (I wonder if she's a virgin...Not that it matters ^_^X.). And it didn't help either that Megumi constantly played on Kaoru's insecurities by flirting outrageously with Kenshin. But in the end I think that Kaoru learned to grudgingly like and respect Megumi.
In the manga, Kaoru was more prone to jealousy fits than in the anime because of Megumi's flirting. It was so funny to watch (I love the anime Katsu episode wherein the two girls turned into their animal counterparts) especially when Kaoru turns SD and takes her anger out on Kenshin (Poor Kenshin). I was mostly amused by their interaction. But in the episode after the goodbye scene (Kaoru moping at the house after Kenshin left), I have to admit, I wasn't at all glad with the way Megumi handled Kaoru. I'm a firm believer that Yahiko was the one who got Kaoru to go after Kenshin and not Megumi. Geez, all she did was berate poor Kaoru and in the process make her even feel worse. It was Yahiko's words (he said something like "You're the only person Kenshin said goodbye to. It must mean leaving you was the hardest thing he's ever had to do," or something like that!) that jolted Kaoru out of her misery, and not Megumi (although I have to grudgingly admit that it did help even just a teeny weeny bit!).
So in the Kyoto arc, the only major interaction between the two girls was that scene below the bridge. I had to admire Megumi there. It's not easy to admit defeat to a younger girl (about Kenshin's feelings, I mean. I believe that until the goodbye episode, Megumi was hoping that she could win Kenshin's heart) but she did. I think it was the smartest thing she ever did in the series. But I didn't like it when she said that she did what she did only for Kenshin's sake and no other's. Doesn't she care, even just a bit about Kaoru? I would've thought that after everything, she and Kaoru would have already established a deeper friendship but to no avail. It seems that if not for Kenshin, she wouldn't even be interested in associating with Kaoru.
My dislike for Megumi reached its height in the Jinchuu arc. Telling Kaoru she's no replacement for Tomoe was really cruel and uncalled for. The Raccoon Girl Shrine said that there were actually two translations of what Megumi said. In the "End of Summer" translation, the line was to be taken as it is. But in the Maigo-chan translation, it could actually be interpreted as Kaoru's situation is not the same as Tomoe's. But in my own humble opinion, based on Megumi's facial expression when she uttered those foul words, I think that the End of Summer translation was more accurate. I really hated Megumi then! I wanted to screech (ala Kaoru) something like "That bloody bitch!!! That whore!!! That harlot!!!.." and every other insulting name I could think of. Hey don't we all say things we don't mean when we're angry? ^_^X And I was really angry that time! So please forgive me for the crude words. I never really meant them, anyway! I mean, to be honest, I really like Megumi as a character. She's way beautiful, sophisticated, bitchy (though I hate it when she bitches around Kaoru. It's okay whenever she does it with Sano and the others but not with Kaoru. You might be thinking that I'm not being fair, but I can't help the way I feel. Sorry! ^_^X), competent, smart, flirty, and sexy. I just don't like the way she sometimes treats Kaoru.
In the end, when she was about to leave for Aizu, she said something like "Kenshin chose not Tomoe, not I (as if she was a contender in the first place!) but you, so keep on smiling for him" (or something like that) to Kaoru, which mellowed my hatred for her until it faded into mere indifference. I guess every anime character had their good moments and that was definitely one of Megumi's. (I really liked the way she was looking at Sano at that scene. Damn, Watsuki-sensei! He didn't do anything about the Sano X Megumi chemistry!)
Puzzling as it may seem, Kaoru never seemed to harbor ill feeling towards Megumi, despite all the hurtful words. Although she claims she hates Megumi, she was saddened by Megumi's departure for Aizu, which I think means that in spite of everything, she actually considers Megumi her friend. I guess that's because Kaoru never really had it in her to hold long grudges.
*New*
I was just watching some RK episodes a while ago and I think I might want to revise the Megumi-Kaoru interaction a bit. Before I go on, I would like to say that my opinion of Megumi in the manga has not changed a bit. But I have softened my views on Megumi in the anime. I watched the episode when Kaoru and Yahiko were about to leave for Kyoto. Megumi, together with Genzai-sensei and the kids, rushed over the river to say goodbye to Kaoru. Based on what I saw there, I believed that Megumi actually cared for Kaoru. Kaoru thanked her putting some sense into her then Megumi said something like, "So you actually understood what I was trying to do!" Kaoru said yes and thanked her again, and Megumi, being a good friend (for once) shooed her away and even good-naturedly teased her about being a silly girl. You know in those moments, I actually like Megumi. Actually, in the anime, I started liking her after that. She was no longer mean to Kaoru after that episode and the two of them seem to get along pretty well. But the manga is a different story altogether. Oh well...
Kaoru and Misao
I think that given enough time, the two of them could be the best of friends. They understand each other (mostly because of their love for Kenshin and Aoshi) and they trust and respect each other. Not only that, they work well together as a team. I loved their fight with Kamatari. They didn't try to outshine each other but instead helped each other. It just goes to show that rivalry between the two of them was almost nonexistent.