The four friends, Rin, Nerine, Mayumi, and Itsuki, decided to have a sleepover at Nerine's house. After Mayumi accidentally activated a magical artifact, however, they found themselves in the middle of a forest. After walking for a while, they found Nerine's parents' house. The four thought they could return home safely, but what appeared in front of them was a younger Sage and Forbesii's fiance, Ai. Then they realized they had been transported to the demon world 20 years in the past. Thanks to the younger Forbesii, who still live in the Demon Palace, they were allowed to stay until they found the magic artifact to return to their original timeline. It is also the day Sage, Nerine's mother, will confess her feelings to Forbesii. However, the confession day has been moved since history has been disrupted by the unexpected appearance of the four. Will they be able to return to the present day without altering the course of history? [Translated and edited from Wikipedia]