Koji Shinomiya is a student at Bell Liberty Academy and holds the dual roles of captain of the archery club and dormitory head. He is known for his stoic demeanor, which often masks a responsible and dependable nature, making him a reliable big‑brother figure among his peers. Standing 178 centimeters tall with short blue hair and purple eyes, his appearance is neat and composed, reflecting the discipline he brings to his duties. His motivation centers on fulfilling his responsibilities with dedication, whether it involves leading the archery team, managing dormitory affairs, or offering quiet support to those around him. Within the story, he serves as a supporting character who interacts with the protagonist Keita Ito and the wider student body, contributing to the ensemble dynamics of the academy. His most notable relationship is his close bond with Takuto Iwai, the art club captain, with whom he shares a deep, trusting connection. While his personal development is understated, his steady leadership and protective instincts become evident over the course of events, and his skill as an archer is frequently highlighted as a mark of his dedication and precision.