In 1924 Tokyo, a young tradesman named Kinnosuke Minoura discovers that his fiancée has been murdered inside a locked room. As he struggles to find the culprit, an elite doctor named Michio Moroto, who has long harbored unrequited feelings for Minoura, offers his assistance to help solve the case. The story follows the two men as they navigate this locked-room mystery, with Moroto’s hidden romantic feelings for Minoura adding a layer of personal tension to their investigative partnership. The narrative unfolds across the streets of 1920s Tokyo, leading toward a climax that determines the destiny between Moroto and Minoura.