Kogoro appears as a guest on a radio show where he discusses the topic of an obnoxious woman living in the apartment above the listener's. Several hours later, apartment resident Kumi goes to yell at her downstairs neighbor Towako. Kumi is furious she was mocked on a radio show, and the two get into an argument. The next morning, Towako's body is discovered, and the police suspect Kumi killed her. Towako is the estranged wife of radio producer Manda. The police believe Manda is also involved in the case, and...

Tamaki Book Cafe manager Yujiro visits Akiko's home to purchase some books. Ten of the books are rare and valuable, but they apparently belong to her hospitalized husband, so Yujiro declines to buy them and tells Akiko to get her husband's permission to sell them. That evening, Sawada arrives at the store and shows Yujiro a picture on his phone of about ten old books and asks how much they're worth. Yujiro tells him it depends on their condition, but they're worth at least two million yen. The next day, the rare books are stolen from Akiko's home. Akiko believes Yujiro stole them, but...