A "Teacher" has a sacred job that protects and guides students. In this world where people who can use magic and people who cannot use magic coexist, Solo is a sorcerer who lives alone. He is also known as No. 0, a skilled assassin who always completes any request he receives. "As part of a certain mission, I am assigned to teach at a magic school, and the teenagers I am assigned to teach are the students of the Class 2D, which is made up of dropouts." While he is desperately playing the role of a teacher in order to complete his mission, a transfer student arrives and the situation takes an unexpected turn... A school fantasy unfolding between a false teacher and the strongest assassin and the most evil students who serve as his "beacon"!