A gamer is magically summoned into a parallel universe, where he is chosen as one of four heroes destined to save the world from its prophesied doom.

Daisuke, Miyako, Iori, Takeru Takashi, Hikari, and Ken must reconcile new responsibilities with their Digimon partners. But Rui Owada, a mysterious young man, appears claiming to be the first human to partner with a Digimon.

Fourteen-year-old Suzuki Iruma has just been abandoned and sold to a demon by his irresponsible parents! Surprisingly, the next thing he knows he's living with the demon who has adopted him as his new grandson, and has been transferred into a school in the demon world where his new "demon" grandfather works as the principal. Thus begins the cowardly Iruma-kun's extraordinary school life among the otherworldly as he faces his true self, takes on challenges, and rises to become someone great.