The scene begins with a mysterious phone conversation about a missing report card. The story then shifts to a vlog recording by a student, So Jung Hwan, where he introduces the 12th-grade Class 4 students of Boseok Boys' High School.
Later, the class discovers that their homeroom teacher has been hospitalized for 15 days, and they will be self-studying during this time. As they settle into their new routine, they start to notice strange occurrences, including an unexplained noise in a student's music demo and a missing carton of milk.
The class then plays a soccer game, but confusion arises when the opposing team claims they only had 10 players, while Class 4 insists they had 11. This leads to a discussion about the class's roster, and they discover that the roll book lists 21 students, but the teacher had mentioned there were only 20.
As the conversation unfolds, the students start to suspect that there may be a ghost or an unknown presence among them, which is hinted at by the mysterious phrase "bunshinsaba" and the fact that the opposing soccer team only saw 20 players. The scene ends with an eerie atmosphere and an unexplained sound, leaving the students wondering what is happening.
Here are the key facts extracted from the text:
1. The homeroom teacher of Class 4 is missing a report card for the March mock exam.
2. The teacher checks the report cards again.
3. A blackout occurs during a phone call.
4. A student, SO JUNG HWAN, is making a vlog about 12th grade Class 4 at Boseok Boys' High School.
5. The vlog features various students in Class 4, including YOON JAE HYUK, HARUTO, KIM JUNKYU, PARK JEONG WOO, YOSHINORI, ASAHI, HYUN SUK, MASHIHO, and BANG YE DAM.
6. The teacher is injured and needs to stay in the hospital for 15 days.
7. The students are left without a substitute teacher for 15 days.
8. The students are confused about how many students are in their class.
9. The teacher had said there were 20 students in the class, but the students count 21.
10. The students wonder if there is an extra student in their class that they don't know about.
11. Someone mentions the possibility of a ghost in the classroom.
12. The students try to figure out who the extra person is by excluding those who didn't play soccer.
13. The students are spooked by strange noises and sounds in the classroom.