名门高中椚椚丘中学的垫底班级3年E班,在新一学年迎来了一个奇怪的老师(二宫和也 配音)。这个老师长着圆圆的黄色大脑袋以及黏滑恶心的触角,原来他就是不久前将月亮炸成月牙的罪魁祸首。日本防务省特种部队的精英乌间惟臣(椎名桔平 饰)向学生们介绍了怪物的情况,他拥有20马赫的超快速度,人类寻常的武器对他完全不起作用。为了阻止怪物一年后摧毁地球的阴谋,人类必须想方设法除掉他。而怪物自告奋勇愿意出任3年E班的班主任,于是乎手无缚鸡之力的学生们担当起刺杀怪物的重任。此后,学生们接受了乌间的严格培训,而杀手比琪(知英 饰)、智能机器人自律思考固定炮台(桥本环奈 饰)、转学生堀部系成(加藤清史郎 饰)以及教官鹰冈明(高岛政伸 饰)等强大对手也相继来到这间暗杀教室内,搞怪的“杀老师”将面临永无止息的刺杀行动…… 本片根据松井优征的超人气漫画改编。The Earth's moon is suddenly 70% smaller and permanently crescent shaped by a devastating and unknown force. For the students of E Class, Kunugigaoka Junior High School, the being responsible is known, as their teacher. The strange and very supportive entity has given the Japanese government a challenge to save the Earth from destruction. It wants to be the teacher of the class with the lowest expectations for success, in anything. The students, armed with special weapons that only harm their teacher, must find a way to kill him before the end of the school year. If not, summer break will be canceled by the end of the world.