Does a two-bedroom apartment in the Tokyo metropolitan area with a rent of 30,000 yen sound too good to be true?

Our hero certainly didn't read the fine print. After renting his dream apartment, Tooru quickly realized that the front door of his new home connects to a dungeon. But it isn't all that bad - after he saves a young knight called Aria, he quickly learns that his home can also be a rest stop for adventurers.