Kindaichi, Miyuki, and Fumi are invited to the Deep Blue Island resort by their senpai, Akane, daughter of the president of the Aizawa Group. The story serves as an alternate retelling of the “Satsuriku no Deep Blue” arc from the 1997 Kindaichi television series. While the three investigate, a group of criminals infiltrates the hotel, posing as waiters, in order to eliminate the members of the Aizawa Group. Unaware of their own boss’s presence, the criminals do not realize that their leader is already on the island, mingling with the very people they intend to kill.