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.

Oh great hero! The evil Demon Lord has once again arisen to terrorise our lands, and we have summoned you to save our people! No, we don't want you to fight the demon lord! Of course not; we're the good guys! What sort of good guys kidnap people from other worlds and force them to take part in wars that have nothing to do with them? That would just be plain evil! We'd be no better than the demons!

Ten years ago, Amelia woke up alone and lost in a broken world where she had to fight for her survival. Now, after reaching the pinnacle of power, defeating the Void itself, and escaping the abyss, she has finally found her way back into the real world. But instead of returning to Earth, she arrives in the land of Vacuos. A fantasy world with magic, monsters, Classes, and Levels. A world that is governed by a System like it were a video game.

They asked Amber to become a magical girl three times. She refused. That only made her more interesting. The fourth time, she asked them.

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?