Shota notices that Nana's work computer is turned on and finds the diary she left behind. As he continues to read it, he receives an email on the computer.

While Shota swears his revenge against Nana's killer, a graduate student, Nikaido, moves into the condo. When Shota finds out that Nikaido is studying AI, Shota asks Nikaido to do something for him.

Shota and the others are surprised to find Kinoshita's room filled with case files related to all the murders, weapons, chemicals, and anatomy charts - what else is she collecting?

Based on the AI results, Shota and Nikaido are confident that Fujii may be the mastermind behind everything. Shota raids Fujii's unit by himself, but someone unexpected awaits him there.

Kusumi has regained consciousness but he looks totally different than he did before the incident. In the meantime, AI analysis shows that four people may have been murdered by the same person.

Someone pushes Kuroshima at a train station and she falls onto the tracks. The residents are suspicious of their new resident, Minami, who exhibits a keen interest in Kuroshima's accident and other cases.

Detective Kamiya becomes the new victim. Since his belongings are taken, Shota thinks that Kamiya may have had information that could lead to the murderer.

Guessing Kuroshima's stalker, Uchiyama, may have been bugging Kuroshima's room, Shota raids Uchiyama's place. Shota finds a disturbing and shocking confession that Uchiyama made by video prior to his death.

Minami suspects Tamiya is the killer of a five-year-old unsolved murder case and questions him. Shota enters Minami's unit and upon seeing a large number of documents in the room, realizes something is up and rushes out of the place.

Kuroshima is likely to be the mastermind of the murder game based on the AI analysis. Shota finds a new clue from the puzzle Nana left, and decides on a plan to lure the mastermind out of hiding.

Shota is attacked by Nikaido and loses consciousness. When he wakes up, he finds Kuroshima also restrained. The whole swap murder game is finally revealed!