High School freshman Kōtarō Satomi wants to start a new life living alone in the tiny Room 106. That lonesome life is immediately broken by the invasion of a group of mysterious girls who all claim Room 106 belongs to them one way or another.
Himari Takakura passes away after going out on a trip with her brothers, twins Kanba and Shōma. She was, however, miraculously saved by a spirit in a penguin-shaped hat. In return for her extended life, the twins must search for an item known as the Penguin Drum with the aid of three penguins, which are visible only to the siblings.
Four men are assigned to the prison: Jūgo, a man who attempted to break out of prison and ended up extending his jail time; Uno, a man who likes to gamble with women; Rock, a man who likes to get into fights; and Nico, a man who likes anime.
Haruka Takayama and Yuu Sonoda were inseparable during their junior high school years, but upon entering their senior high school, they end up being seated on opposite sides of the classroom. Having to spend time with more friends, the two decide to do something to make their relationship special.
Set in the Shinigami technical school for weapon meisters, the series revolves around 3 groups of each a weapon meister and a human weapon. Trying to make the latter a "Death Scythe" and thus fit for use by the Shinigami, they must collect the souls of 99 evil humans and 1 witch.