凤来高中3年D班的班主任九条里奈,是放弃贴近时代、贴近学生的化学教师。毕业典礼那天被“班里的某个学生”推下去,然后时光倒流,站在讲台上,眼前看到的是一年后杀害自己的“30名嫌疑人”。她下定“决心”,颠覆教室、人生,冒着生命危险挑战面对学生。。“Praise be to the cinema: the law is not said, it is seen and heard. A story is born and given to us. This is how, through an image, life is resuscitated”. (Jean-Luc Godard, 1985)。