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.

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.