An original story based on the characters of Hayamine Kaoru's mystery novel of the same name. Naito Naito, a second year high school student who has the ability to survive in any situation, teams up with Ryuo Soya, a talented boy whose father is the head of the Ryuo Group conglomerate. The two of them and others challenge "Area Z", a game created by the genius creator only known as "Kurii Eita". Can they complete their mission to save the city within 6 hours?