Opera Kobayashi, once a renowned detective, was stripped of his supernatural Toys during a clash with phantom thief L five years before the main storyline. This defeat shifted his path from active investigation to mentoring the junior detective team Milky Holmes—Sherlock Shellingford, Nero Yuzurizaki, Hercule Barton, and Cordelia Glauca—training them in detective techniques and Toy mastery. Though absent physically in the anime’s first two seasons, his legacy lingers through references and a fleeting image.

As the protagonist of the PlayStation Portable visual novels, he confronts the Thieves’ Empire under Arsène, unraveling mysteries through strategic leadership. These games delve into his tactical mind and establish Cordelia Glauca’s discipleship, rooted in her reverence for his past triumphs.

The *Alternative* OVA specials reunite him with Milky Holmes in London, partnering with Toy user Lily Adler to thwart the Thieves’ Empire, mirroring the games’ serious tone and spotlighting his calculated methods.

In the spin-off *Futari wa Milky Holmes*, set two years post-series, he resurfaces as a supporting figure, underscoring his enduring impact on the detective world. The finale *Psycho’s Greeting* humorously disrupts his attempt to congratulate the team’s graduation, interrupted by Henriette Mystère’s abrupt dismissal.

His vanished Toys remain an enigmatic thread across adaptations, their exact powers undisclosed. Yet his influence as a fallen prodigy and steadfast mentor persists, anchoring Milky Holmes’ growth through his unseen but indelible guidance.