The body of Nito Tsuyoshi, the president of a real estate company, is discovered. The Special Investigation Team is present, but the body is located under the stairs and it's hard to determine if it was a murder or an accident. The team set off to investigate the truth behind the incident. Munakata, however, is the one to discover that the incident may be connected to the death of someone else 30 years ago. It's a case tying Showa and Heisei together as Japan enters the Reiwa era.