One day, Arisu, a new student, joins Haruka's class. She suddenly says, "It's you. You're the culprit. Come with me now!" Haruka is surrounded by a strange whirl and sent to... When he regains his consciousness, he finds himself being in his town. But it looks somewhat different. Yes, he time slipped back to 20 years ago! According to Arisu, she is now investigating some mysterious phenomenon. If she can't solve it soon, it will cause a devastating damage to the world... Like this, Arisu and Haruka start investigating the cause of the phenomenon together...
