The Detective Boys met a group of elder detectives known as The Elderly Detective League. The Elderly Detective League run into a murder case and the Detectives Boys will compete to solve the case before the other detectives.

Amuro witnesses a woman pushed from the top of the stairs at Haido Park. However, he doesn't see the culprit's face. The unconscious and gravely injured woman pushed from the stairs is FBI Agent Jodie's friend and Haido Elementary School teacher, Natsuko. Later, Inspector Megure and the police question her coworker Sugamoto, who tried to give Natsuko a ride home, and Ueno and Kandachi, parents of students with appointments to see Natsuko...