Movie
Description
Itona Horibe is a student who transfers into Kunugigaoka Middle School's Class 3-E as the second assassin sent to kill the octopus-like teacher, Korosensei. He is the only son of a family that ran a small electronics factory producing parts for smartphones. After the family business went bankrupt due to competition from larger corporations, Itona was abandoned and sent to live with relatives, leaving him vulnerable to bullying from his peers. This period of hardship and the taunts of being a weakling with nothing created a deep-seated obsession with power and an intense fear of being weak or losing. Itona was later found by a man known as Shiro, who saw potential in the boy's desperation and tenacity. Shiro took him in and subjected Itona to experimental body modification, transplanting tentacle cells onto his head to turn him into a living weapon designed to destroy Korosensei. As part of this manipulation, Shiro fabricated a story for Itona, leading him to believe he was Korosensei's younger brother.

Upon his initial introduction to Class 3-E, Itona's personality is defined by a cold and brutal fixation on strength. He possesses a brutally honest and direct way of speaking, showing little interest in anyone he deems weaker than himself. His only goal is to prove he is the strongest by killing Korosensei, an obsession fueled by the tentacles that have begun to consume his consciousness. During this period, he also unconsciously mimics some of Korosensei's interests, such as a fondness for sweets and adult magazines, much to the shock of his classmates. However, after Shiro abandons him and he is rescued and befriended by the students of Class 3-E, particularly Ryoma Terasaka and his friends, Itona undergoes a significant transformation. He becomes more mellow, humble, and sociable, learning to acknowledge that others can be stronger than him while retaining his characteristic blunt honesty. His desire to kill Korosensei shifts from a self-centered quest for power to a collaborative effort as a member of the class.

Itona's primary role in the story is initially that of a secondary antagonist and a formidable rival to both Korosensei and the students. He serves as a tool for Shiro's schemes to eliminate the teacher, demonstrating the dangerous potential of artificially implanted tentacles. Following his redemption arc, his role changes to that of a valuable and loyal member of Class 3-E, contributing his unique skills to their ongoing assassination attempts.

His key relationships are central to his development. His relationship with Shiro is purely exploitative; he is a disposable asset, and Shiro abandons him without hesitation when he fails. The bond he forms with the class bully Terasaka and his gang is crucial to his rehabilitation. It is their rough but sincere encouragement and acceptance that help him let go of his obsession with power. He is often seen in their company, participating in class activities and even collaborating on perverse projects like building a remote-controlled tank to look up girls' skirts, which helps him bond with the other boys. His relationship with Korosensei evolves from a violent rivalry based on a fabricated brotherhood to one of a student and teacher, with Itona coming to respect the creature he was meant to kill. After the tentacles are removed, he also reconnects with his estranged father, and they work together to rebuild the family electronics business.

Itona's most notable ability is derived from the tentacles implanted on his head, which grant him superhuman speed and strength, allowing him to match and even injure Korosensei. These tentacles can be upgraded by Shiro for different combat situations. However, the tentacles also cause a severe mental drain, reducing his intelligence to a single-minded focus on power, and trigger a fatal rejection reaction in his body. After Korosensei successfully removes the tentacles to save his life, Itona loses this immense combat power but his natural intelligence and creativity return. He reveals himself to be a genius in electronics and craftsmanship, a skill he inherited from his family's business. He uses this talent to build an array of gadgets for the class, including custom drones and radio-controlled vehicles for surveillance, information gathering, and assassination support, quickly becoming the class's unofficial tech expert. Although his enhanced physical abilities gradually fade after the tentacles are removed, he remains in good physical condition and is considered one of the stronger students in the class.