S.3.O.K.J.1.N is the world renowned assassin, he has been credited with over 400 kills and he never fails a mission but this time he has been sent to a university for an undercover mission to assassinate the principle of the school who has been hiding from S.3.O.K.J.1.N's employers. Will this mission be a success or will S.3.O.K.J.1.N start having feelings for a certain clumsy boy known as Kim Namjoon?

They tell you one thing when you become a teacher: Leave your personal problems at home. Kim Namjoon's problem, however, is also in his workplace. The problem being none other than his coworker, housemate and best friend, Kim Seokjin. Namjoon's daily life consists of teaching English at Hiteu High School of the Arts for Healing. Among that, he resolves teenage drama and has to handle the teasing from his fellow teachers and students regarding his closeness to Seokjin. Every day he's telling everyone, and himself, that he's just a friend. Kim Seokjin has been only that since the day they've met.