Seong-beom, a tutoring teacher, visits his old middle school to retrieve a graduation certificate required by his academy director — only to discover that his student record no longer exists in the system. With the help of So-eun, a former classmate now teaching at the school, he begins to trace the missing files. In doing so, he finds that another name has also been erased: Shim Won-mo, a friend from middle school. Won-mo was two years older than the rest of his class, adopted, and always on the margins — a boy who eventually dropped out after running away from home more than once. Seong-beom had watched Won-mo drift and struggle, yet never reached out. Now, after all these years, news arrives that Won-mo has taken his own life.