Shirō Hitsujikai is the primary antagonist and student council president of Onigashima High School, an institution established to oppose Otogi Academy. He possesses platinum-colored hair and distinctive violet eyes with snake-like pupils, typically dressed in a white uniform accented with yellow. His middle school persona included glasses, aiding his facade as a model student. His deceptive personality masks a sadistic core; outwardly polite, he revels in inflicting psychological and physical torment. This sadism manifested when he forced Ryōko Ōkami, his former middle school girlfriend, to watch him brutally beat her admirer, Ryōshi Morino. Overconfidence often leads him to underestimate opponents, causing tactical errors.

His past relationship with Ryōko ended when he attempted to sexually assault her. Afterwards, he spread false accusations that destroyed her reputation, causing her peers to abandon her. This betrayal forced Ryōko to transfer schools, leaving lasting trauma and a deep fear of him. Years later, Shirō reenters Ryōko’s life upon discovering her involvement with the Otogi Bank, Otogi Academy's student assistance group. As the unseen orchestrator of Onigashima High's coordinated attacks against the bank, he leverages his authority to escalate hostilities. He specifically exploits Ryōko’s lingering trauma by deploying a subordinate, Reiko Kokonoh, who falsely claims to be another victim. Manipulating Ryōko’s empathy, Shirō lures her into a trap, resulting in her kidnapping.

His character draws inspiration from "The Boy Who Cried Wolf," emphasizing themes of deceit and consequences. His name translates to "White Shepherd," contrasting with his predatory actions.