The protagonist, Yagumo Sanada, carries the scars of a dark past—kidnapped by terrorists as a child abroad, sold to an anti-government group in a conflict zone, and forced to become a child soldier.

Having returned to Japan on his own, he found himself with only an elementary school dropout’s education.

Working as a high school guard to reintegrate into society, he tried to adapt to a peaceful daily life, despite students fearing the scar on his face from his battlefield days.

Then, a sudden darkness engulfed his surroundings.

When he awoke, he was on the first floor of a dungeon, surrounded by the academy’s teachers and students. As they reeled in confusion, a woman’s voice, claiming to be the Succubus Queen, echoed in their minds.

The Succubus Queen declared that the academy’s men had been chosen as testers for a dungeon created to facilitate the demon tribe’s invasion of Earth.

Yes, only the men. The female students and teachers were imprisoned in another dimension as Slaves.

These women could be saved by purchasing them with DP (Dungeon Points), earned by exchanging magic stones obtained from defeating dungeon monsters.

Purchased Slaves are bound to absolute obedience to their master, branded with a lust tattoo. In return, they can return to the surface with their master when the test ends. But unsold Slaves will be disposed of.

“High school girls as Slaves? Oh, really?”

Motivated by the noble cause of saving lives, Yagumo resolves to build a slave harem.

“Take up arms, kill enemies, and get women as a reward. Just like back then. No problem at all.”

Armed with the skills and resolve to fight alone, Yagumo slays more monsters than anyone, venturing deeper into the dungeon than anyone else.

And so, he acquires the academy’s most beautiful girl, a bunny-eared beauty from another world, and more, one after another.