Mito Yamada, older sister to Hanappe Yamada and daughter of Michiyo and Kyuta Yamada, lives with her family. She habitually teases Hanappe playfully, especially when he returns bruised from fights. This teasing escalates into an incident where Hanappe retaliates by grabbing her breast after she prods his sore face. Her existence shifts dramatically with the arrival of demons Ophisto Bazooka and Mephist Dance. The lesbian demon Mephist Dance fixates on Mito, overpowers her resistance through supernatural force, and converts her into a demon. This conversion reshapes Mito's behavior and desires. After their home transforms into a demonic space, Dance subjects Mito to bondage and whipping. Despite Hanappe's interventions, Mito develops an enjoyment of this sadomasochistic dynamic with the demon. She, alongside her parents, fully embraces their demonic existence, actively rejecting Hanappe's attempts to restore their humanity and obstructing his efforts against the demons, expressing a firm preference for their new life. When the demons use Mito and Michiyo as hostages to compel Hanappe's surrender during a confrontation involving holy artifacts, the tactic fails; both women willingly side with the demons, affirming their allegiance to the demonic life over family. This choice contributes to Hanappe's subsequent emotional collapse and suicide attempt. Mito does not appear again in the narrative. In the manga adaptation, her arc similarly involves a sexual transformation by Dance through yuri themes, though specific additional developments beyond this are not detailed.