After the disappearance of his parents, Suzuki Tooru was all over the place and somehow ended up as a caretaker of a school dormitory in Tachikawa. The dorm building is all tattered. Its student boarders are all weirdos. And of course, there are rumors about ghosts haunting it too. Turns out, that dorm is connected to another world! Although Tooru doesn’t have a single friend in class, he can always just go to the dungeon to slay monsters and level-up. There, he befriended a slime, a female knight, and even a female sorcerer ♪ Thus, he begins another day of after-school club activities in another world!

A college student buys a new apartment dirt cheap and the reason was that once the front door is opened from the inside it connect to a dungeon in another world instead so he goes to an adventure in the dungeon and meet new companions which treat him as a the Great Sage