Memumemu is a hapless demon assigned to claim human souls, though she has yet to succeed. She fixates on high school student Hyōta Kohinata, repeatedly visiting his apartment intending to seduce him and secure his soul. Her consistent failures stem from her profound incompetence as a demon.

Her minimal magical abilities carry a literal cost: using her scant power physically diminishes her size. Consuming small amounts of food or energy drinks restores her stature and strength. Inherent clumsiness and a distinct lack of demonic talent ensure her plans unravel.

Timid and emotionally fragile, Memumemu cries easily and exhibits a servile nature. Despite her fearfulness, she seizes any perceived opportunity to advance her goal of taking Hyōta's soul. She clings to persistent, though unfounded, optimism about her mission.

Memumemu develops complex ties within Hyōta's apartment. A connection forms with Hyōta, who feels sympathy for her despite her designs on him. She harbors deep terror of the landlady, Anzu Itsuki's mother, viewing her as a formidable "boss" due to the landlady's unconsciously potent demonic talents. Memumemu's presence often sparks misunderstandings that cast Hyōta in a negative light. Her role centers on comedic interactions arising from her bungled demonic duties and her navigation of relationships with Hyōta, Anzu, and the landlady.