Yotsuya Mamoru, the late father of Miko and Kyousuke, met an untimely end before the story’s events. A year prior, his decision to eat a chestnut pudding Miko eagerly anticipated sparked a fierce quarrel, leaving their relationship strained. His sudden passing cemented this rift, burdening Miko with unresolved regret.

In death, his spirit manifests as serene, free of the malice or distortions plaguing other entities, reflecting his enduring benevolence. Miko encounters him multiple times, most notably when she leaves a pudding at the family altar. This offering becomes a conduit for reconciliation: he expresses remorse, and she extends forgiveness, dissolving their lingering tension.

Mamoru’s bond with his children echoes his living role—a guardian whose watchful presence persists beyond life, quietly shielding them. His death and the unresolved argument anchor the narrative’s exploration of regret and healing. His name, "Mamoru" (to protect), mirrors his paternal duty, while "Yotsuya," combining the kanji for "four" and "valley," subtly ties to the story’s spiritual foundations.