Having regained her confidence after solving numerous cases together with Saruwatari (Maruyama Ryuhei), Sukui (Taira Yuna) has finally decided to return to her job as a police officer. At a celebration for her return, Sukui confides in Saruwatari that she wants to investigate the Yanaka Child Murders, the last unsolved case investigated by her father, Inukai Jūshiro (Yamaguchi Makiya), who died in the line of duty. The key to the case lies with Kito Yasuomi (Takahashi Katsunori), Jūshiro's former partner and head of the Metropolitan Police Department's First Investigative Division. Saruwatari and Sukui go to meet Kito at the Metropolitan Police Department, but...