Kozue Takanashi, ten years Souta Takanashi’s senior, balances part-time shifts at Wagnaria family restaurant with teaching self-defense courses at 25. Her restless energy and quick boredom propel her to seek constant amusement, often fixating on others—particularly Souta—whose patience she tests with her clinginess. Though capable of professionalism in her instructor role, her personal life lacks structure, clashing with Souta’s disciplined demeanor and fueling his wariness toward older women. Romantic relationships crumble under her insatiable need for attention and fleeting commitment, leaving her to drown disappointments or monotony in alcohol. Yet her chaotic existence coexists with a stubborn dedication to employment, hinting at unexpected responsibility. Family interactions weave affection with friction: she needles Souta relentlessly yet leans on him for companionship, oscillating between playful teasing and rare, genuine concern for her siblings. When their mother’s reappearance stirs dormant family tensions, Kozue’s role intensifies, pushing the Takanashis to face fractured dynamics. Her erratic habits—drinking sprees, impulsive antics—persist as both comedic foils and emotional triggers, underscoring the family’s tangled bonds. While her growth remains stagnant, her presence amplifies themes of duty and connection, anchoring the narrative in the messy, enduring ties that bind the Takanashis together.