Mamimi’s background is largely ambiguous, but she is hinted to have an unstable home life, leading to her delinquent behavior and tendency to escape into fantasy. She is implied to have been bullied in school, which could explain her aversion to attending classes. Her relationship with Tasuku was seemingly a source of comfort, but after he left, she filled the void with anything she could attach herself to including Naota, objects, and even destructive tendencies like arson.

Her name appearing in katakana rather than kanji in certain scenes suggests that she may not be entirely Japanese, further adding to her sense of displacement and detachment from her surroundings.

Mamimi has shoulder-length auburn hair with bangs that often cover her eyes, contributing to her distant and unreadable expression. She is usually seen wearing her school uniform, a dark blue dress with a white collar, though she rarely attends school. A notable accessory is her ever-present cigarette, a symbol of her detachment and escapism. Her body language is often slouched or lethargic, reflecting her aimless lifestyle.

Mamimi is melancholic, withdrawn, and emotionally dependent. She displays an almost childlike attachment to things and people, often calling them “Ta-kun” in an attempt to fill the void left by Tasuku’s absence. While she initially appears gentle and quiet, her character carries darker undertones, including an unhealthy obsession with fire. She has been known to set small fires out of boredom or emotional distress, suggesting a subconscious desire for destruction or rebirth.

She also exhibits passive manipulation, particularly with Naota. She treats him as a substitute for Tasuku, using him for comfort but losing interest when he begins to assert his own independence. While not outright malicious, she is self-absorbed, often too lost in her own world to recognize how her actions affect those around her.

• Connection to Naota
  Mamimi frequently hangs around Naota, treating him as a surrogate for Tasuku. She often teases him, displays affection toward him, and attempts to maintain a dependent relationship, though it is largely one-sided. Her influence over Naota diminishes as he gains independence, leading to her eventual emotional detachment from him.

• Fire and Destruction
  Mamimi’s fascination with fire is a recurring theme. She is first seen setting fire to an abandoned school, hinting at her history of arson. Her destructive tendencies escalate when she adopts a mysterious robot, Canti Mk. II, and begins feeding it broken technology and encouraging it to destroy things. This serves as an indirect parallel to Naota’s own transformation, as both are being shaped by forces outside of their control.

• Symbol of Lost Innocence
  Throughout FLCL, Mamimi represents a form of stagnation and escapism. While other characters, particularly Naota, go through significant changes, Mamimi remains largely the same wandering through life aimlessly, avoiding responsibility, and clinging to the past. Her final scene in the series suggests that she eventually leaves town to find her own path, though her fate remains ambiguous.