The protagonist, Akumo, is an adventurer.

As a support class who assists his companions from the rear, he is scorned and treated as a nuisance to the party.

He is finally abandoned deep within a dungeon, left in a desperate situation where returning on his own is impossible.

"If I can't go back, I might as well push forward," a desperate Akumo resolves.

Miraculously, however, when he reached the final destination, he was granted the qualification to become the dungeon's master... a Dungeon Master.

He will rebuild "The Withered Cave" from scratch into the strongest dungeon.

Adventurers, once his comrades, will invade. He'll repel the very ones who scorned and abandoned him, giving them their just deserts.

And primarily, this is a laid-back and carefree dungeon management story.