The story is set at Myoujou Academy, a private girls' boarding school. The 10th year's Kurogumi class has 12 assassins with their sights on one target, Haru Ichinose. Tokaku Azuma is a recent transfer student who is also targeting Ichinose, but she gradually develops feelings for Ichinose.

[Source: Anime News Network]

The story of the original episode takes place on an uninhabited island, where the cast of the Black Class must fight each other in a survival game. The goal of the game is to capture Haru, and Tokazu says she can't afford to lose.

[Source: Anime News Network]