10 days away from graduation, homeroom teacher Hiiragi, stands in front of his students and tells them they have now become his hostages. He says that no one can leave unless someone can tell him the reason behind a past student's suicide.

Art Teacher, Hiiragi Ibuki, has worked at his current school for 2 years. He is the homeroom teacher of Class 3A. With only 10 days until graduation, Hiiragi stands in front of his 29 students and tells them "From now on, you are all my hostages". He starts his lesson, which will only end if someone can tell him the reason behind a past students death, who had committed suicide a few months before, but if they give a wrong answer, someone will die.—Amber Steininger