Itona Horibe

Itona keeps his platinum hair short and spiked, tinted a pale bluish white in the anime, and later covers it with a broad bandana. His eyes are a sharp light blue, drawn amber in the animation. Though on the short side, he carries a solidly muscled frame.

Bullying and abandonment left Itona craving strength and loathing any hint of weakness or defeat, which is why he let Shiro graft tentacles onto him and fixated on killing the formidable Korosensei to prove he was the strongest alive. Blunt to the point of harshness, he speaks his mind without softening it. While the tentacles controlled him he even aped Korosensei's tastes, from a sweet tooth to a fondness for gravure magazines. After Shiro discards him and Terasaka's crew take him in, he mellows considerably, growing humble enough to admit when others outmatch him while keeping his frankness. He proves observant and inventive as he settles in, though his perverted streak never fully leaves, as when he offers to drive a self-built tank under the girls' skirts.

Itona is the son of the man who once ran the Horibe Electronics factory. When the company went bankrupt his father abandoned him to an uncle's care, and the bullying that followed hardened his obsession with power and winning. Shiro discovered him one night and promised to make him the strongest man alive, equipping him with artificial tentacles. He storms into Class 3-E by smashing through the back wall, declares himself Korosensei's blood brother, and duels the teacher as his hair splits into whipping tentacles. Korosensei ultimately traps him in his own molted skin and hurls him from the ring. Further schemes follow, including a rigged pool trap sprung through a manipulated Terasaka, but each ends in failure.

The repeated defeats let the tentacles devour Itona's mind, and when Shiro coldly abandons him he rampages through the town's electronics stores until Class 3-E, tired of being used, rescues him and Korosensei removes the parasitic growths before they can kill him. Grateful, Itona finally joins the class for good and falls in with Terasaka's group. Even without the tentacles he keeps sharp athletic ability, memorably felling Class A's pole with a towering leap at the athletic festival, and his real intelligence, long stifled, shines through his engineering. He builds and customizes remote-controlled vehicles for reconnaissance and safely strips the explosive collars off himself and his classmates after the Reaper kidnaps them. During the Class 3-E civil war he sides with the faction set on killing Korosensei, guards Rinka Hayami, and is cut down by Maehara. Years later he works at his father's rebuilt factory, ready to lean on Muramatsu and Yoshida should it ever collapse again.