Kazuma Kurosawa, owner of Uta Island's Opera House Hotel, is a middle-aged man bearing self-inflicted cheek scars from his daughter Mika's suicide four years prior. He projects a good-natured façade that occasionally fractures, revealing a frightening demeanor. A former director of the Genso Theater Group and ranked among Japan's top five, his theatrical mastery is exemplified by directing eight distinct productions of "The Phantom of the Opera." A decade before the hotel events, he acquired the island with its Georgian-style vacation home, spending six years transforming it into the hotel-theater complex.

His family life is marked by tragedy: Mika's death profoundly shaped him, his second marriage is to Shizuka Hibiki, and they have a son, Eiji Kiryu. Eiji, once Kazuma's acting genius disciple, suffered severe facial burns in a Karuizawa theater company fire. Following the initial Opera House Murder Case, Kazuma's concealed darker facets surface during subsequent hotel incidents. His involvement evolves complexly, shifting from suspect to a figure whose history catalyzes new tragedies.

Kazuma dies during the incident known as Opera House, The Third Murder, accidentally falling from a cliff into the sea. Though his body remains undiscovered, survival is deemed impossible. This pivotal death draws other characters back to the hotel. Early narrative plans included Rio Kanai dying alongside him, but this was omitted. His name combines "harmony, peace" (和) and "horse" (馬) for Kazuma, while Kurosawa signifies "black" (黒) and "marsh" (沢).