It is Monday, the fifth day into the investigation and still, they do not know if there are actually ghosts or spirits or just ground subsidence. That very day, Mai, Kuroda, Matsuzaki, John, Takigawa, Hara and Shibuya were summoned by the principal. They were supposed to be hypnotised just for that moment.
Mai and John met up with Shibuya in the old school building. They set up the chair and marked the space where the chair was, set up the camera and the radar tracker and sealed up all the doors and signed on the plywood. The next day she went back to meet Shibuya at his van where she saw his actual assistant. Shibuya wanted to prove that it was ground subsidence. The entry points of that room were sealed off so no one could get in or out because they would have to break open the plywood and it would never be repaired as there were signatures on them.
The actual reason behind all this is ground subsidence. Kuroda was the one behind all this. She was unconciously believed in the spirits, the poltergeist usually occurred mostly around young teenagers. She was a girl with a strong spirit sense, these phenomenons occurs from the subconcious in times of extreme stress. Shibuya believes that Kuroda is a latent psychic; she has a certain level of having the ability to move things by thought which is a mental ability.
The door that was not able to open was because of a nail that jammed it. It was because of the insult that Matsuzaki said to Kuroda that made her do this little prank to scare Matsuzaki. The video was erased and not done by some supernatural being that tried to stop the video. The video was erased by Kuroda. Everything was done by Kuroda because she wanted attention, she was an attention seeker. So the case was closed but only they know the truth about the "ghost hunting".
Mai returns to school after the ghost hunting and get a call from Shibuya. He invites her to continue working for him at the Shibuya Psychic Research. She willingly agrees to continue as a part-time worker there.