Mimori is a supporting character introduced in the third season of the story. She is depicted as a shy and withdrawn young girl who struggles to speak up and often mumbles to herself. She spends most of her time alone in her room, and few people pay attention to her except for her stepbrother Hirotoshi. After her mother remarries, Mimori moves in with her stepfather and Hirotoshi, a reclusive man who initially becomes fixated on her but eventually develops a genuine protective bond. Mimori's loneliness and neglect lead her to self-harm.

Her role in the story begins when she becomes possessed by a Nokker, a parasitic entity that twists its hosts into foes. As a result, she becomes the second Nokker-infested person that Fushi encounters and the first he must fight directly. Under the Nokker's control, she exhibits unnatural, contorted movements and attacks Fushi with a feral intensity. Her physical appearance is unremarkable: she wears a white blouse and a skirt with suspenders, and her black hair is cut just above her earlobes with slightly frayed bangs and lighter tips.

Key relationships center on Hirotoshi. Despite his questionable past and the uneasy implications of his early interest in her, he proves to be a caring brother who helps Mimori choose to return to life after the possession is resolved. Her parents are largely negligent, leaving Hirotoshi as the only consistent figure in her life. Mimori does not possess any supernatural abilities of her own; the Nokker possession grants her temporary, distorted physical capabilities. Her development moves from extreme isolation and vulnerability to a brief period of being a threat, then ultimately to being saved and given a chance to live again. Her narrative underscores themes of neglect, the corrosive effect of loneliness, and the destructive influence of the Nokkers.