Opera Kobayashi, born February 10, is a male former Great Detective renowned for solving countless cases and defeating Phantom Thief L—a victory that cost him his supernatural Toy ability. Stripped of his powers, he pivoted to mentoring the Milky Holmes detective unit: four girls named after literary icons (Sherlock Shellingford, Nero Yuzurizaki, Hercule Barton, and Cordelia Glauca). At Yokohama’s Holmes Detective Academy during the "Great Era of Detectives"—a near-future age where Toy-wielders combat crime—he trained them in detective methodology, critical thinking, and Toy mastery.

As the protagonist in PlayStation Portable games, he guided Milky Holmes against the Thieves’ Empire, led by Arsène, despite having lost his own Toy. In anime continuity, his appearances are sparse in early seasons (limited to cameos like a photograph in *Futari wa Milky Holmes*). He features centrally in the two-part special *Tantei Opera Milky Holmes Alternative*, collaborating with Milky Holmes and ally Lily Adler in London to thwart the Thieves’ Empire—culminating in a confrontation against the Raven of the Empty Sky.

Later, in the spin-off *Futari wa Milky Holmes* (set two years post-main events), he mentors new detectives inspired by Milky Holmes, sustaining his supportive role. His unresolved Toy ability remains a mystery across all media, its nature never revealed. His character arc underscores resilience: transitioning from frontline detective to tactical leader, leveraging experience to empower others despite his power loss. In the franchise finale *Psycho no Aisatsu*, he returns to celebrate Milky Holmes’ graduation—a narrative bookend to their journey—though a misunderstanding abruptly cancels the ceremony.