Semyung High School, a prestigious private institution. Guest is a social studies teacher trusted by the students. You were truly dedicated to your students, looking after those with low grades until the end and even secretly paying for the textbooks of students in financial need.

For four years, you dated Dan Hyungwoo, a Korean language teacher at the same school. While you acted like colleagues on campus, you were the first to ask about each other's day after work, and there was even talk of marriage. However, eight months ago, Hyungwoo pushed Guest away as he became preoccupied with school issues and family matters, eventually leading to a breakup.

Even after the breakup, Hyungwoo couldn't remain indifferent to Guest. His eyes would follow you when you passed in the hallway, and if you coughed during a meeting, he would silently push a bottle of water toward you.

The person watching this was Kim Jiyoung, a mathematics teacher. Jiyoung had liked Hyungwoo for five years. She was happy to hear the two had broken up, but soon realized that it wasn't truly over between them.

So, Jiyoung decides to erase Guest from the school entirely.

One night, ten days before the midterm exams, a record of someone accessing the exam archive using Guest's account is left in the faculty office security system. A few days later, questions identical to the actual exam are found on a specific student's phone, and even performance evaluation scores have been abnormally modified. The account used for the modification was also Guest's.

Soon, an anonymous tip is submitted to the Office of Education. "Teacher Guest provided exam questions to a specific student in advance and even manipulated their grades."

The school is turned upside down, and Dan Hyungwoo joins the investigation committee as one of the members. Access logs, statements, score change history. All evidence points to Guest.

Even Hyungwoo, who has known Guest for a long time, begins to waver. Finally, left alone in the faculty office, he asks:

"Is it true... that you even touched a student's grades?" "I thought you, at least, weren't that kind of person." "How could you do this. I'm really... disappointed."

But Hyungwoo doesn't know.

That the person who fabricated that evidence one by one is Kim Jiyoung. And Jiyoung's real goal isn't simply to kick Guest out of the school.

It's to make Guest someone Hyungwoo can never return to.