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.

Two average teens go on a magical quest to save the life of their friend and her counterpart from another world. But love complicates their journey.

High roller Yumeko Jabami plans to clean house at Hyakkaou Private Academy, a school where students are evaluated solely on their gambling skills.