Among the students, Aizawa hates Onizuka the most. Eventually all the students end up liking Onizuka, but Aizawa refuses to let go her hatred of Onizuka. She becomes obsessed with getting Onizuka fired, by any means necessary. Since manga issue 14 she has dyed her hair blue.
Uehara comes from a rich family, and her mother happens to be head of the PTA. At first she seems to be a stuck up spoiled brat, but she actually has a good side. She eventually gives up on trying to get Onizuka fired, but still thinks of him as a nuisance. She has had bad experiences with her brother and a past boyfriend, so she doesn't have much trust in boys, and usually sticks to her girlfriends.
Kikuchi, like Urumi, is a genius with an IQ of 180. He's a computer expert and proficient in Karate. He can be pretty evil if he has to, but unlike Urumi, he has morals. Kikuchi is the most level headed character in the series, and stays pretty cool even in extreme situations. He's always serious and not the type to joke around.
Murai is the typical badass. He talks big and has a short temper, but on the inside he's actually a mama's boy. When he gets out of line his mom puts him back in place. He's basically the class bully. Definitely the most mischievous of the students, but he isn't really bright enough to cause any serious trouble.
Yoshikawa is the class dork. He's a master at videogames, and loves anime. He doesn't really get pushed around by the guys, but the girls pick on him non-stop. He's attempted suicide a few times, but Onizuka managed to stop or save him each time. He's the first student at Tokyo Kissho Academy to become friends with Onizuka. He often goes to Onizuka's room to help Onizuka out with videogames.
Mayu is the grandson of Sakurai Ryoko, so despite being one of the biggest troublemakers at Tokyo Kissho Academy, he gets away with almost anything. Like Urumi, Mayu hadn't been going to school, but was called in by Aizawa to deal with Onizuka. Mayu is a drug addict, and apparently is proficient in Karate, since he handles himself very well in fights. He loves to make awful practical jokes, and is a real danger to his enemies and also, himself.