Shinji Ito transfers to a new high school determined to reinvent himself as a prominent delinquent. Before their school debut, he encounters Takashi Mitsuhashi at a salon, where both commit to hairstyle changes for their new identities. Ito adopts a sharply spiky hairstyle requiring substantial hair gel, earning him the nickname "Kappa." Standing 180 cm tall (205 cm including his hair), his physical stature is imposing. His personality starkly contrasts with Mitsuhashi’s cunning, defined by an unwavering sense of justice and moral righteousness. He consistently intervenes against bullies and unfair situations, prioritizing fairness in confrontations. This principle shapes his fighting style—relying on brute strength and endurance while accepting hits instead of evasion, leading to frequent injuries, particularly when defending others or facing multiple opponents. Early in his delinquent journey, he rescues former sukeban girl Kyoko Hayakawa from thugs, sparking her affection and a romantic relationship. Kyoko’s parents approve, partly relieved she avoids involvement with Mitsuhashi. Around Kyoko, Ito reveals a softer, emotional side, often becoming flustered or affectionate. His commitment to protecting friends and allies remains steadfast. He engages in large-scale conflicts like the Akehisa High confrontation and takes significant risks to aid others, including Mitsuhashi. During the Saipan arc, he intervenes to prevent an attempted rape. His loyalty extends to enduring financial hardship, struggling to afford gifts for Kyoko during a broke period. Family dynamics, including interactions with his parents, are briefly explored. His background merges typical high school experiences with delinquent activities. Through repeated clashes with rivals like Imai and Sagara, he undergoes subtle maturation, yet his core traits—honorable combat, protectiveness, and moral integrity—endure across all media adaptations.