Mamoru Yotsuya is a deceased character in the story, having died roughly a year before the events of the series begin. He was the husband of Touko Yotsuya and the father of Miko Yotsuya and her younger brother Kyousuke Yotsuya. During his life, he appeared to be an ordinary father who wore glasses and behaved like a normal human being. He showed no signs of hostility toward living beings even after death, and his ghost retains a benign, everyday demeanor. His sudden and unexpected passing left a significant emotional impact on his daughter Miko, as the two had a trivial argument over him eating her pudding shortly before he died. Miko was unable to reconcile with him before his death, and she has carried regret over that unresolved conflict ever since. Throughout the narrative, Mamoru appears as a spirit that Miko can see, yet he does not menace her or demand attention the way many other ghosts do. His presence serves as a poignant reminder of her loss and the unfinished business between them, contributing to Miko’s emotional development as she grapples with her ability to see the supernatural. Mamoru does not possess any extraordinary abilities as a ghost; he simply exists as a spectral figure that appears indistinguishable from a living person. His role in the story is largely emotional and thematic, anchoring Miko’s backstory and motivating her internal journey.