Koji Majima is a supporting character from Kamen Rider Agito who comes from a family of doctors. He develops a friendship with Mana Kazaya and becomes an avid admirer of Kaoru Kino, a figure whose charisma initially draws Koji into the orbit of the series' central conflicts. His personal philosophy is guided by a deep-seated belief that no one can live without meaningful connections to others. Beyond his medical lineage, Koji is also a capable individual with proficient computer hacking skills, which he occasionally employs to assist people like Aki Sakaki. His character arc is primarily defined by a single profound act of selflessness toward Ryo Ashihara, the host of Kamen Rider Gills. After Ryo sustains life-threatening injuries in a battle with Another Agito, Shoichi Tsugami instructs Koji to transfer his own dormant Seed of Agito to save Ryo. Koji willingly performs this transfer, sacrificing his own potential to become a Kamen Rider entirely for the sake of another person. This donation not only saves Ryo's life but also allows him to evolve into the enhanced form of Kamen Rider Exceed Gills. Through this decisive action, Koji moves from being a passive admirer of the superpowered conflict to a pivotal figure in the heroes' cause, embodying the themes of compassion and human connection. His primary notable ability is his status as a bearer of the Agito seed, a genetic marker that endows humans with the latent potential for great power.