Arc was an ordinary young woman from Earth when she was summoned to an icy hell where she fought for her survival in the name of training to become a hero. Now, after defeating the Overlord itself and achieving the status of hero, she leaves with the goal of enjoying her freedom. She arrives at Arlas, a fantasy world with magic and monsters, a world with numbers, tiers, and classes, a world governed by the System that summoned her.

Ilea likes punching things. And eating. Unfortunately, there aren’t too many career options for hungry brawlers. Instead, the plan is to quit her crappy fast-food job, go to college, and become a fully functioning member of society. Essentially—a fate worse than death.

She's unlike any one or any thing else: a Non-Standard Leashed-Intelligence Cybernetic Enforcer aka NSLICE-00P. The first of her kind, she's let loose into a universe of superheroes on behalf of her sinister masters to destroy all who oppose them. And everything's going according to plan—until NSLICE-00P gets hacked and sent into the past to kill her own creator before he creates her. Obeying orders as always, she wastes the poor guy. Unfortunately, there are consequences to initiating a reality-breaking time paradox. The most significant: total ejection from that reality.

The usual result of a human taking a runaway semitruck head-on is a very sudden, very fast track to the pearly gates. But for one newly noncorporeal man, there's another option: become a dungeon. Feeling sorry for the desperate angel assigned to him, the man relents. Heck, if it doesn't work out, he can always chat with Saint Peter about it later. Next thing you know, he's a dungeon. Admittedly, a small run-down, somewhat unimpressive dungeon (more of a house, actually), but you gotta start somewhere, right?

When Kers is reborn as a dungeon core, he finds himself stuck in the most improbable of places: a cloud. High in the sky and far away from the usual solid resources, Kers must face the obvious question: How is a dungeon to build itself without wood or stone? Luckily, Kers has the sarcastic (and sometimes helpful) fairy Selena to help him get his bearings. Together, the pair delight in exploring Kers’ weird existence, creating novel mobs, and enticing adventures to plumb the lofty heights of his floors.