Fourteen-year-old Iruma Suzuki 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 Netherworld 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.

Not every party treats you like a hero—especially when you’re a lowly red mage like Yuke. So, after years of constant ridicule by his A-rank party members, he ditches them. Searching for a new party, he reunites with former students Marina, Silk, and Rain, and joins their group. But on a quest to conquer the world’s greatest dungeon, they become entangled in chaos that threatens the world.