Onizuka used to be Yankee, a Japanese delinquent. His best friend is Danma Ryuji and with him he's part of the Onibaku Duo (Oni for Onizuka and Baku for Bakudan which means Bomb.) Back in his younger days, Onizuka used to have a lot of street fights with people trying to be better than him. As the Onibaku was reputed unbeatable, his opponents were not above Kick the Dog
and Moral Event Horizon
on him and his friends. Bad luck for them, Onizuka used to get a little Ax-Crazy
when pushed too much. He then left Shonan, faking his death in front of his friends. He then moved to Tokyo. Since then, Onizuka became a teacher and softened up a bit.
You really want him to be your Teacher!!!
16 years old Onizuka in Early Years.
- A Man Is Not a Virgin: He believes this at his core and wants to get rid of it...badly.
- This is the main plot point of Early Years, when he's not bashing someone's skull.
- Anti-Hero: He cleaned up his act as a street-brawling punk but his tough upbringing still shows up when he gets pissed off.
- Ax-Crazy: In his younger days, he was really scary when angered. You can see shades of this in GTO and Shonan 14 Days.
- Blood Knight: When he was younger. He's softened a bit since GTO.
- Badass: Seems to be made of this.
- Bash Brothers: With Damna Ryuji, in Shonan Jun'ai Gumi/GTO Early Years.
- Berserk Button: Just try to harm any of his students, pals, or Azusa.
- Catchphrase: "Onizuka Eikichi, 22 years old." before declaring his motivations to do something. "Onizuka Eikichi, 24 years old." In Paradise Lost.
- Character Development: In Early Years he starts as a street punk, but as the battles continues he starts seeing that it's not worthy of his friends being hurt and on the verge of dying. That's when he starts thinking of giving up being a Yankee.
- Chivalrous Pervert: He had plenty of occasions to have his way with some female students (like Urumi), but he still prefers to have consensual sex with somebody that really means something to him. Like Azusa.
- Determinator: And how! Could easily turn into a Juggernaut. Heck, you can throw literally everything at this guy and he still wont be stopped. Not even a broken clotted blood vessel in his brain could keep him down for long.
- Disappeared Dad: Eikichi's mother raised him alone, he never saw his father since several years.
- Faking the Dead: Jumped from the top of a building with Ryuji to try and put an end to the endless gang fighting at the end of Early Years, it worked. However, their friends see throught the charade because they used a fake knife to stab eachother.
- Former Teen Rebel
- Hands-On Approach: Towards Fuyutsuki, to teach her how to game.
- Implacable Man: Nothing stops him, nothing.
- Jerk with a Heart of Gold: Less of a heart than usual examples, but unlike most teachers in the show, Onizuka cares deeply about the welfare of his students and will see to it that they become better people under his watchful eye.
- Like Brother and Sister: With Fujisaki Shinomi, which annoy her to no end. Because of this, Onizuka never date her.
- And according to Shinomi herself, this his how he views Urumi Kanzaki too, which annoy her as much as Shinomi.
- Lovable Sex Maniac
- Luminescent Blush: Whenever presented with the possibility of sex. Or just when Fuyutsuki hugs him.
- Made of Iron: Eventually subverted when it turns out his body really has been undergoing extreme damage and much more will kill him.
- Naïve Newcomer: Averted. He is in fact pretty Genre Savvy.
- One-Man Army: In Early Years.Still is, if the situation calls for.
- Papa Wolf: May God have mercy on you if you ever intend to cause harm to his students!
- Pay Evil unto Evil: Sometimes in GTO. Very often during Early Years.
- Proud to Be a Geek: Oh yeah!
- Smoking Is Cool
- Split Personality: Never seen in GTO. But in Early Years, it's often pointed out that a pissed off Onizuka is really a different man that the happy go lucky guy we know.
- When he met him, Ryuji was convinced that it was a some kind of Super-Powered Evil Side or whatnot and that he had to make him fight seriously to see it. They become friends before he see it, though.
- Suplex Finisher: Fond of doing German Suplexes. It's probably his Finishing Move!
- Trickster Mentor
- Underestimating Badassery: ALL THE TIME in Early Years, bigger opponents understimate Onizuka because he's a 16 years old kid. Just ask Machida 
- Unluckily Lucky: He's sometimes this. In one example from the anime, he comes across a large bag of money (that's good), which he spends all at once. It turns out the money was the school's field trip funds, which was planted on him in order to frame him for embezzling (that's bad). He somehow manages to convince the school not to fire him (that's good), but only by pledging an even more expensive field trip which he can't possibly afford (that's bad). He then fails to earn anything near the amount needed, only to win a car in an unrelated lottery (that's good). He then lends the car to a complete stranger, with no guarantees that the stranger will return it on time, if ever (that's bad). The stranger turns out to have been hired by the person trying to frame Onizuka (that's bad), but has a change of heart and returns the car anyway (that's good). At the last possible minute, naturally.
- Warrior Therapist: Especially in Early Years.
- Would Hit a Girl: A variation. While he isn't the type to beat up girls, Eikichi doesn't go easy on females who cross the line, especially in the live action series where he didnt hesitate to punish Miyabi by holding her by the feet from a building's ledge until she apologized for bullying Noboru.
- Wrestler in All of Us: See Suplex Finisher above.
Best friend of Onizuka and the other member of the Onibaku Duo. Met Eikichi in High School, they started as enemies when Danma saw Onizuka's Ax-Crazy
self beating someone to a pulp. He then wanted to anger Onizuka enough to see it again and fight him. They became friends since and he used to be The Lancer
to Onizuka.After finding a girlfriend and moving to Tokyo, he took his family's bike business.
Get on his bad side and you're in for big trouble.
Teacher in Tsujido High School, where Onizuka and Damna are. She met Ryuji during summer vacations before they moved to Tsujido and she'll fall in love with him. After many trials she'll decide to date Ryuji. She has a troubled past ( Her boyfriend died in a bike crash a few years before, on chrismas day. ) She'll finally marry Ryuji, with just the two of them during a summer night before leaving him, finding unfair to rob him of all his teen years and friends.
Ryuji haves good tastes for women, indeed.
- Dark and Troubled Past: Her boyfriend died on Xmas day in a bike crash, she have trouble dealing with the lost, even when she's with Ryuji.
- Love Interest: Well, she's Ryuji's first love after all.
- Meganekko: Meet all the requirements.
- Morality Pet: Ryuji's, he really changes after he got with her.
- Put on a Bus: Takes a train and leaves Shonan and Ryuji for good.
- The Bus Came Back: Comes back to Shonan after living 6 months with her parents, she meets Ryuji again as friends.
- Reason Before Honor: Why she leaves Ryuji, it's more reasonable to let him live his youth than living with him and rob him of his teenage years.
- Teacher/Student Romance: With Ryuji.
- Tender Tears: When she rides a train and leaves Ryuji
- Will They or Won't They?: They did kiss.They never had sex though, she left before and Ryuji backed out when he got the chance.
Ryuji's current girlfriend. She was the girlfriend of Akutsu, leader of 2nd Generation Midnight Angels. She was so scared of him and of everything he made her do that she created a litteral Split Personality
named Yaksha to protect her from the trauma. Ryuji and Onizuka break the curse and she turns out to be a very cheerful girl. She lives with Ryuji in GTO.
Ryuji's wife, for real this time.
Former Rival of Onizuka during his delinquent times, Saejima was the kind of guy who would do anything to accomplish his goals. He destroyed the lower half of the last guy's face who challenged him, everyone was then scared shitless of him after that. A while after, he tried to challenge the Onibaku. He managed to force a good friend of Onizuka betray him but he was defeated anyway by Onizuka himself. 5 years later he became a cop. He makes cameos in GTO.
- Anti-Hero: Type V. He is possibly the most corrupt and violent cop that can be found in any manga. However, at the end of day, he is still one of Onizuka's best, most trusted and loyal friends. If Onizuka somehow has to call for his help, he would be by his side until the end. Was still as crazy and violent before becoming a cop.
- Ax-Crazy: Like a good deal of the Early Years villains, he was.
- Still is. In fact, if you somehow manage to push Onizuka to the point of running to this guy for help, you are basically fucked. God has mercy, Onizuka knows mercy, HE DOESN'T!
- Bad Ass: Being one of Onizuka's partners in crime in their early years, he kicks ass!
- Dirty Cop
- Defeat Means Friendship
- Demoted to Extra
- Face of a Thug: Even his whole family is scared shitless of him, even when he behave.
- Red Baron: Kamakura's Wild Dog.
- Red Oni, Blue Oni: Blue to Kamata's red.
- The Rival: To Onizuka in Early Years, before Defeat Means Friendship.
- Pre-Asskicking One-Liner: "Yo Eikichi, mind if I sit your class here? I can help make your point! Son of a bitch can't demand nothing from me!". Welcome to your nightmare, Suguru...
Seajima's former partner when he was a street punk. The other Kamakura's Wild Dog. Teamed up with Saejima against the Onibaku. He got beaten by Danma and became friend with him and Onizuka. He's most of them time a secondary character, but receive a lot of character development during the Natsu Return Arc ( told mostly from his point of view), dealing with his best friend supposed to be dead Natsu. He moves to the USA after that. He's a straight up guy but is not above fighting dirty if the situation calls for it.
- A Day in the Limelight: The Natsu Return arc from Early Years, told from his own point of view.
- Ax-Crazy: Probably rivals the Onibaku in this.
- Bad Ass: Teamed up with Saejima, so obviously.
- Hot-Blooded: Goes with the Seiyuu.
- Put on a Bus: He goes to the USA, never seen again.
- The Bus Came Back: In Ino-Head Gargoyle, he returns to Japan to become a police officer and is Seajima's cop partner.
- Red Oni, Blue Oni: The Red to Saejima's blue. Saejima is calm compared to Kamata.
Friend of Onizuka, Danma and all of the gang in Early Years. She met them in High School, she was the fat kid everything mocked. But she fell in love with Onizuka. Two years later she came into Onizuka's new High School after a big diet making her really beautiful. However, Onizuka did treat her very much the same way as before, with utmost respect, going as far as treating her like a sister. Which Shinomi hated since it ruined her chance to get with him. When Onizuka and Ryuji fakes their death at the end of Early Years, she's left heartbroken and doesn't appear in GTO at all. until GTO Shonan 14 days when Onizuka returns to Shonan and meet up with her again.
Eikichi, a teacher ? Yeah, right. Gimme a break.
- Badass: Well, she was like a female Onizuka back then.
- Get a Hold of Yourself Man: To Onizuka after he consider giving up fighting for good.
- Formerly Fat: As hot as Shinomi is in Early Years and Shonan 14 Days, she was fat when Eikichi met her. After saving her from rape when she was 13, she fell in love with him. 2 years later she came back in the same High School as him, now smoking hot.
- Love Interest: For Onizuka in Early Years.
- Not So Different: with Urumi Kanzaki, since their relationship with Onizuka never really evolved for both girls.
- Plucky Girl: Goes without saying.
- Rape as Drama: She fell to that during Early Years, courtesy of Akira Takezawa from the same gang as her, The Idaten.
- Furthermore, if a girl leaves the gang. She's to be raped by all the male members. As a way to make sure no girls try to leave. Shinomi leaves anyway.
- Tsundere: A very strong Type-A.
Legendary Leader of the Midnight Angels Gang, Senior of Onizuka and Danma. He first met them in Bad Company, a short gaiden published in Early Years' last volume.He died two years before Early Years started. Was rumored to be unbeatable in street fighting and in bike racing. Onizuka inherited his bike and coat, making him his successor.