Kei Kikuno attends a vocational school as a student. For her part-time job, she works as a contract killer. She is excellent at her job and never gets scared by anyone. One day, she receives the most challenging request.
With her gloomy demeanor, Sawako has a hard time fitting in. But when an outgoing classmate approaches her, life takes a turn for the better.
On-call substitute doctor Shugo suddenly finds himself faced with a terrifying criminal in a clown mask. The assailant demands that Shugo treat injured high school student Hitomi. The perpetrator sets siege to the building and Shugo finds himself confined with 64 unknown patients.
