Touma Funasaka is offered an unusual recommendation for his next school by his homeroom teacher. The school in question is Toyashihara Academy—a national, full-boarding institution that accepts only students through recommendation, with no general admissions. It also happens to be his teacher's alma mater.

The low tuition and full-boarding system seemed like the perfect opportunity, so Touma decides to enroll. But what awaited him was an academy that defied common sense—a place built atop a vast underground dungeon, ruled by sex and violence.

Though bewildered at first, Toma quickly adapts to the decadent academy life. While indulging in a corrupt and hedonistic youth, he also joins comrades to form a party and challenge the dungeon's depths!