Tokaku Azuma has just transferred to the elite Myoujou Academy, a private girls' boarding school. But there's a catch: she, along with 11 of her fellow students in Class Black, is an assassin taking part in the challenge to kill their sweet-natured classmate, Haru Ichinose. Whoever succeeds will be granted their deepest desire, no matter the difficulty or cost. However, each assassin only gets one chance; if they fai...