Detective Ryo Hoshino of the Metropolitan Police Department’s First Investigation Division sports purple-tinted brown hair and eyes, typically clad in his division’s standard suit. His serious demeanor and unwavering adherence to protocol define his professional persona, particularly evident in his dismissive interactions with former colleague Haru Kato, whose idealism he frequently criticizes as naive.

Ryo and Haru’s shared history as partners in the First Investigation Division fractures after Haru’s departure, marked by Ryo’s sharp critiques and refusal to share case details. Tensions ease when Ryo uncovers evidence that Haru resigned voluntarily, prompting a gradual shift from hostility to guarded respect. By later encounters, his overt antagonism fades, reflecting a tempered understanding of Haru’s choices.

Anchored in organizational discipline, Ryo prioritizes protocol over personal connections—a principle echoed in his name’s meaning (“cool, refreshing”) and his composed exterior. Key moments, such as his rigid adherence to procedure during the Classic Car Festival bomb threat and his role in exposing internal police misconduct, highlight his dual focus on institutional order and uncovering hidden truths.

The provided sources do not detail his involvement in spin-offs, films, or OVAs.