Momose and Shirosaki's next business trip takes them to Shirosaki's hometown in Akita Prefecture. Shirosaki is triggered by the trauma of being snatched up by a namahage demon as a child during the local festival, but he is able to complete their field research safely. Previously, Shirosaki received a phone call from his grandmother saying, "I have something I want to show you," so the two head to Shirosaki's family home. At his grandmother's suggestion, they look at and reminisce over old photo albums when his grandmother reveals that "what she wants to show" is something Shirosaki never expected.

Inside a train station with high passenger foot traffic, Momose and Shirosaki look upon a giant advertisement. The release day of Momose's first ad, which he created for the aquarium, has finally come. On his way to the aquarium, Momose spots a man at a nearby café who looks like his previous boss, Kurono. Even when he enters the aquarium, he ends up remembering Kurono. While accompanying Momose, Shirosaki notices a suspicious man. The envelope that the man holds has the name of Momose's previous company written on it….