Satoru Kido is a private investigator hired to locate a missing ruby ring at the secluded Nakakouji estate mansion. His professional approach emphasizes personal freedom and cultivates a "cool detective" image, frequently smoking cigarettes. This persona aids his interactions with female clients, facilitating information gathering through charm and perceived sophistication. He has brown hair, grey eyes, stands 1.77 meters tall, and weighs 64 kilograms. Arriving on the isolated island, he experiences an unsettling sense of familiarity with the surroundings, an intuition that proves significant. During his investigation involving interactions with residents like the young mistress Ayano Nakakouji, maid Nozomi Watase, a butler, a manservant, and a tutor, he uncovers a personal connection: the mansion is his familial home, and he is the missing heir. This discovery unfolds amidst explicit encounters with the women residing there. Three months after the events, which concluded with the mansion's destruction by fire, he rescued Nozomi Watase from the inferno. His involvement with the estate and its aftermath continues, indicating unresolved developments.