Here are some simple character descriptions from Vampire Knight. I included brief descriptions of appearances along with the pictures, because before I knew the story well enough, I would confuse some characters.
The Day Class
Yuki Cross
Yuki was attacked by a crazed vampire at the age of 5, but was saved by Kaname and brought to Headmaster Cross. She is now 15 years old. Yuki is a strict enforcer of the rules between the day and night classes. She is very responsible and kind. She’s in love with Kaname, because he saved her and visited her as she grew older, but she is currently pretty shy around him. Since Kaname adores her, she is reluctantly accepted by the night class. She cared for Zero the night Headmaster Cross brought him home 4 years ago and has been his close friend ever since. She refuses to let Zero turn into a Level E vampire, and promises him that she’ll personally kill him if that ever happens. She sympathizes with the pain Zero must be going through with craving blood, and since he can’t handle the blood tablets, she persuades him to take her blood whenever he needs it.
Appearance: Yuki has short dark hair and brown eyes. So far the only female character with those looks.
Zero Kiryu
Zero’s family was slaughtered by pure blood vampire 4 years before the present story. Headmaster Cross found him and took him in. He knew Zero would eventually become a vampire since he was bitten in the attack, so he had the tattoo put on Zero’s neck as a sort of spell in hopes of preventing the change. Since it didn’t work, the tattoo now acts as a safety measure for when he gets out of control; all someone has to do is touch the tattoo with a metal charm that has Zero’s blood on it, which is on a bracelet Yuki wears. Zero comes from a long line of famous vampire hunters. He was trained in his hunting skills by Yagari Toga. Zero has a seething hatred towards vampires and therefore is constantly struggling with himself. He doesn’t like Kaname coming near Yuki, and is pretty protective of her. He hates himself for attacking Yuki and continually drinking from her, but his cravings are unbearable. He dreams of the day he can take his revenge on the woman who killed his family.
Appearance: Zero has gray eyes and shortish pale hair that lies flat and thin around his head. He has a black tattoo on the side of his neck.
Yori
Yuki's friend and roommate. Seems to be a calm girl and a good friend to Yuki.
Appearance: Has pale hair cut in a short bob.
The Night Class
Kuran Kaname
Kaname is the president of Night Class and a seemingly gentle person. He is one of few pure blood vampires in existence and is therefore highly respected by the night class. He had fallen for Yuki ever since he saved her as a child and always watches over her. He wants to be closer to her, but senses how shy she is about it. Kaname knew of Zero eventually becoming a vampire and despises him for feeding from Yuki. Kaname has asked Headmaster Cross to put Zero in the night class, but to no avail. Kaname would do away with Zero if it wouldn’t hurt Yuki so badly. When Shizuka comes to Cross Academy, Kaname commits the greatest sin among vampires by killing her, a pure blood. Kaname is told by Kain that he saw Zero near her crumbles body, and he decides to report to the Council of Ancients that Zero killed Shizuka.
Appearance: Kaname has brown/sort of red eyes and dark longish hair that usually hangs messily around his face.
Aido Hanabusa
Aido is a flirt and often jokes about feeding from girls. He once fed from a small wound on Yuki's hand, which infuriated Kaname. Aido hangs around with his cousin and friend, Kain. Aido has demonstrated that he has the power to turn water into ice, or to just create ice out of thin air. The adoring girls of the Day Class call him "Idol". Aido witnesses Kaname killing Shizuka, but doesn't tell anyone of what he saw.
Appearance: Aido has messy light hair and blue eyes.
Kain Akatsuki
Kain is Aido’s cousin and roommate. He’s usually hanging around with idol and lets him do as he pleases. The fan girls in the Day Class nicknamed him "Wild", because of he looks wild. When Shizuka died, Kain, saw Zero holding his gun in the room where she was killed, and reports to Kaname what he saw.
Appearance: Kain is tall and has similar hair as Aido’s; messy and pale. His eyes are brown. He doesn’t usually wear his tie with his school uniform and leaves his shirt unbuttoned near the collar.
Souen Ruka
Ruka is a friend of Kaname’s. She doesn’t seem to think too highly of humans or why vampires would want to socialize with them. She is very possessive of Kaname because she is in love with him. He once drank her blood, which is said to create strong feelings for the one whose blood is being taken. Ruka believes that to be true, since she now cares so much for Kaname. She tries to offer Kaname her blood again, but he politely declines, which hurts her feelings.
Appearance: Ruka has long, wavy, pale hair.
Ichijo Takuma
Ichijo is the vice president of the Night Class and seems to be a kind and friendly person.
Appearance: Ichijo has shortish pale hair.
Shiki Senri
Shiki is Ichijo’s friend. He works as a model.
Appearance: Shiki has shortish dark hair that’s messy and in his face.
Seiren
Seiren is a girl in the Night Class who sometimes hangs around with Kaname.
Appearance: Seiren has short pale hair that is cut straight around her chin.
Rima Tooya
Rima seems to hang around Shiki and goes out to hunt Level E vampires when asked to.
Appearance: Rima has pale hair that she wears in high pigtails.
Maria Kurenai
Maria is a frail girl and a distant relative of Shizuka. When first introduced to the story, Maria's body is being used by the spirit of Shizuka (with the permission of Maria). She causes trouble for being so forward with the other night class students and by running around campus during the day. She has an interest in Yuki and tells her on more than one occasion that she wants her blood. Once Shizuka is done using Maria's body, she returns to her normal self and goes home with her parents.
Appearance: Maria has long, straight, pale hair with a little bun on the side.
Others
Headmaster Cross
Headmaster Cross is (obviously) the headmaster of the school. He is slightly effeminate and is likely a homosexual. He strongly believes in peace between humans and vampires. He offers the night class for vampires to educate them in hopes they will promote peaceful coexistence with humans. He thinks of Yuki and Zero as his children, but is usually pretty strict with Zero, since he knows that he’s struggling to suppress his urge for blood.
Appearance: Headmaster Cross has long pale hair that he keeps tied back. He wears glasses and fine clothes.
Yagari Toga
Yagari was Zero’s teacher in vampire hunting as a child. He is currently the top vampire hunter, since the Kiryu family is no longer around. He lost an eye to a vampire attack because Zero pleaded for him to have mercy on the turned human he was going to kill. Yagari was sent to Cross Academy by someone to see if Zero was under control, and to eliminate him if he wasn’t. During his time at Cross Academy, he teaches a Night Class. He had originally brought Zero to Headmaster Cross and wanted him to care for Zero after his attack.
Appearance: Yagari has sloppy dark hair and wears an eye patch over his bad eye. He smokes cigarettes.
Shizuka Hiou
Shizuka is the pure blood vampire that killed Zero parents and took his twin brother Ichiru away. It is rumored among other vampires that she went mad and disappeared after attacking the Kiryuu family. She held a grudge against the Kiryuu family after they followed orders to kill her former human vampire lover. She took Ichiru as a servant and cared for him, and turned Zero into a vampire. By killing the Kiryuu's, she became wanted by the Council of Ancients for viciously slaughtering humans. She returns to Cross Academy by possessing the body of a girl name Maria Kurenai. She tells Yuki she can save Zero, but Yuki would either have to kill Kaname or give her like over to her. Shizuka returns to her real body in order to gain strength from taking Yuki's blood, but Zero stops her. She then drinks from Zero, but when she leaves him, she is caught by Kaname and killed by him.
Appearance: Shizuka has long, straight, pale hair, and always wears a kimono.
Ichiru Kiryuu
Ichiru is Zero's twin brother who was kidnapped by Shizuka when they were children. Ichiru was being trained to become a vampire hunter like Zero, but was prone to illness, so his parents decided he couldn't become a hunter. Ichiru was very close to Zero, but envied him for being healthy. One day Ichiru was seduced away from his family by Shizuka, and after drinking her blood, became her faithful and loving servant. He returned with Shizuka when she slaughtered their parents, but didn't seem to care. He comes with Shizuka when she comes to Cross Academy, and tells Zero that he hates him. When he finds Zero with Shizuka's dead body, he believes Zero killed her, and takes off. Soon enough he returns and joins the day class.
Appearance: Ichiru looks just like Zero, but has no tattoo on his neck. His hair may be a little longer than Zero's.