Kankin inran yûgi

Original title: 監禁いんらん遊戯

Haruka decides to buy a vacation home to reclaim time with her husband, who is recovering from an injury. When she visits the property to inspect it, she is led by the caretaker to the basement, where she finds an old diary. Inside is a candid account of the experiences of the diary's owner, Utako Maruyama.