The Locked Evening Study Classroom

There is a classroom in Nanchuan No.7 High School that has long been sealed with iron chains. Rumors say that on the night before every monthly exam, the sound of turning pages can be heard from that classroom, answers for the next day's exam appear on the blackboard, and one person who should have walked out of the teaching building goes missing. Xu Chen, a transfer student in his sophomore year, originally just wanted to get through to graduation quietly. But during his first evening self-study duty, he received a seating chart from the locked classroom, listing the names of all classmates, with his own name already framed in black. Old school rules, missing graduates, roll calls in late-night broadcasts, and a sign-in sheet that always has one extra person... As the entire school begins to resemble a huge haunted examination hall, Xu Chen realizes that what is truly locked is never that classroom, but everyone who wants to leave alive.