Ushimitsu

She is the ghost that used to be a student in PK Academy 20 years ago. She is skilled in piano but she passed away due to a disease 20 years ago. After dying, like most of the ghost she too lost her memory of when she was alive and was completely attached to the piano in the PK Academy's music rooom due to her strong passion for it. After Toritsuka and Kusuo's persuasion, she decided to move on to after life even though Reita told her she can be with the piano in temple. The next day, her piano was taken down the school and Reita asked Kusuo to take the piano and teleport it to his room in the temple. However, she didn't came back after that.

Trivia

 * The piano was actually owned by her family and after she died, her parents decided to donate it to the school.