Yuma Himeno, sporting pink hair and attending Moe Junior High, develops romantic feelings for her neighbor Makoto. Discovering his relationship with classmate Emma plunges her into distress, setting her story in motion.

Her path shifts when she encounters Ton, an extraterrestrial pig merchant. He grants her a magical lipstick housing Leap, a fairy-like creature. Using this lipstick, Yuma physically transforms into Mia, an older, sexually mature version of herself. As Mia, she pursues Makoto, leveraging her adult appearance to attract him.

Adopting the Mia persona, Yuma fiercely competes with Emma for Makoto's affection. Their rivalry ignites a public dance-off at a disco and escalates further when Emma deploys military-grade weaponry during a chase. In retaliation, Mia pilots a stolen giant robot. Following this conflict, Mia isolates Makoto and initiates a sexual encounter.

A critical limitation of the magical lipstick surfaces during this intimacy: Yuma reverts to her original child form upon experiencing sexual climax. This sudden transformation forces her to flee after knocking out a bewildered Makoto, highlighting the instability of her magical solution and the stark contrast between her youthful self and the adult persona.

Yuma's rollerblading hobby and persistent jealousy toward Emma remain constant. Her actions consistently stem from a desire to bridge the gap between her adolescent feelings and the adult relationships she observes but cannot naturally access. The magical intervention ultimately creates complications that underscore the disconnect between her physical transformation and emotional maturity.