Kanaka Nanase, the protagonist’s elder half-sister, originates from her father’s first marriage to an extraterrestrial woman. Though decades older in lived experience, her body remains trapped in a childlike physique—a consequence of relativistic time dilation during interstellar travel. This dissonance between her true age and youthful exterior fuels persistent frustration as she battles societal perceptions to uphold her authority as the family’s eldest sibling.

Her arrival on Earth begins in disorientation, spurring impulsive reactions to her father’s new human family and life. Rash decisions escalate tensions, culminating in a physical clash that accidentally wounds her half-sibling. Gradually acclimating, she forges friendships like her bond with classmate Hajime Yagi, whose support anchors her integration into human social circles.

Her demeanor teeters between playful mischief and burgeoning responsibility. Though prone to bratty outbursts, she nurtures a fierce protectiveness toward her younger sister, straining to reconcile her desire for maturity with the constraints of her diminutive form.

Family strife defines her past: her father’s choice to abandon spacefaring life for Earth, his remarriage to a human, and her alien mother’s cosmic obligations fracture their relationships. Initial bitterness softens into acceptance as she mends ties with her father and cautiously embraces her Earth-born family.

Later, she temporarily leaves Earth to join her mother, a starship commander, navigating the stars. Centuries later, she returns to reunite with her sister and friends, prioritizing cherished bonds over cosmic duty. Her arc mirrors the challenges of adaptation, identity, and the fragile bridges between blended families across time and space.