This side mission will become available after purifying all three torii gates at Shiroyama Shrine. To start this mission talk to the spirit of a repair worker you can meet near the entrance to The Hotel.
A spirit in front of a hotel tells Akito and KK about the hotel's oddly-structured fourth floor. The pair decide to investigate.
From: Repair Worker
The entrance to the hotel is right next to the spirit from whom you will receive this mission. Enter the building, kill the Visitor you come across on the first floor and get into the elevator. The elevator will take you straight to the fourth floor of the hotel. Proceed to the end of the hallway and you should notice a suspicious-looking wall there.
Activate the Spirit Vision and you will thus reveal a yokai and a hidden passage. Approach it and absorb it. You will receive a Magatama.
Enter the hidden room and read the Man's Note lying on the table standing next to the bed.
Return to the elevator, ride it down and go outside. Inform the spirit of what you've figured out. The spirit will thank you for your help, this simple mission will end and you'll be rewarded.
On the hotel's fourth floor, Akito and KK encounter a yokai known as a nurikabe pretending to be a wall to block the entrance to a room. Akito absorbs it and gains a magatama.
