Teichi Gakuen is an advanced school in Tokyo with a high rate of students going on to the University of Tokyo. The 3rd year "D" group of students has an excellent academic record. However all the teachers who were in charge of the 3rd year D group have broken down shortly and have retired. In fact, some students in this class have mentally tortured the teachers like it was a game. In a way that is close to a criminal, students crush their homeroom teachers without getting their hands dirty. In such a twisted environment can the new homeroom teacher, Keio Yoshizawa Tsuneo played by Tanaka, arrives. Yoshizawa smiles and smiles all the time. Even if a student makes a mean statement or asks a question, he answers with a smile. Even if he is physically attacked by the student, he is smiling for some reason. Somehow Yoshizawa knows the students' private information. Despite this the students' behavior escalates, and they plan to kill him. Why did Yoshizawa come to this school? How long will he endure the traps set by his students? Teachers and students battle each other in a closed space called a school.
