Yuusaku Kudou features in the short story "Ten Planets in the Night Sky." When he vanishes, his wife Yukiko Kudo searches for him, relying on a mysterious coded message he left. Their young son Shinichi Kudo provides unintentional clues essential to cracking the code, demonstrating the child's early deductive abilities shaped by his father. During these events, Yusaku is occupied writing manuscripts. This leads him to disconnect his phone, causing him to miss communications, including police thanks for helping chase away a thief. In "The Wandering Red Butterfly," he appears as Yusaku Kitakata, a detective who receives daily anonymous phone calls presenting new cases. He solves each case methodically while the caller's identity forms the central mystery driving the narrative. No further appearances occur in the anthology.