The junior high school I attended was famous "bad middle school" locally.
It was a junior high school which was rough roughly, such as breaking a container or making a smoking campaign against a teacher who inconvenienced neighbors.
Because there is such an environment, empty classrooms and libraries that are not used are locked up.
And there is another "toilet" which is prohibited to use normally.
A key is hanging on the table and no one can enter it.
The toilet is near the shoe casket on the first floor and the student who has been going to school passes through the toilet and surely climbs the stairs and goes to the classroom.
This is the premise.
From here onwards is an unforgettable story experienced by me and a friend.
On that day, it was late for club activities teacher to come over than usual and I and my friends were free so I was exploring school.
After passing around inside the school building casually past the toilet with that key
"Concon"
And I heard a sound.
It