Hazumu Osaragi starts as an effeminate high school boy possessing a gentle nature and deep passion for floriculture. Bullied in childhood for feminine traits, Hazumu consistently relied on protection from tomboy friend Tomari Kurusu. A pivotal moment occurs when, rejected after confessing feelings to classmate Yasuna Kamiizumi, Hazumu climbs Mount Kashima and is fatally crushed by an alien spacecraft. The alien, Hitoshi Sora, revives Hazumu but reconstructs the body as biologically female using female "life grains" and a female gynoid blueprint, resulting in complete anatomical and DNA-level sex transformation.

Post-transformation, Hazumu resigns to living as a girl with minimal protest, exhibiting pre-existing feminine traits like sensitivity and expressiveness. Initial adjustment challenges involve unfamiliarity with feminine etiquette, modesty norms, and clothing like bras. Adaptation pace varies: the manga depicts quicker adjustment with less external guidance, while the anime emphasizes prolonged cluelessness, with Tomari actively teaching feminine behaviors. Hazumu consistently retains the masculine first-person pronoun "boku."

Hazumu's core personality persists—kind, selfless, and indecisive, especially regarding romantic feelings. This indecision fuels a love triangle between Hazumu, Yasuna (who reveals her affections post-transformation), and Tomari (who acknowledges childhood feelings). Yasuna's unique visual impairment—seeing males as blurred figures except partially for pre-transition Hazumu—facilitates her attraction. Tomari struggles with jealousy yet remains protective.

Character development shows increasing comfort with female identity through mannerisms and fashion, aided by a mother who enthusiastically provides feminine clothing. Core relationships evolve: a childhood promise to be Tomari's "bride" resurfaces, while Yasuna's devotion intensifies. Narrative paths diverge later:
- **Manga**: Hazumu faces a fatal "life grain" deficiency one month post-revival. After accepting impending death, Tomari donates life grains during a rooftop fall, saving Hazumu. This culminates in Hazumu choosing Tomari romantically.
- **Anime**: No life-threatening crisis occurs. Hazumu chooses Yasuna to cure her worsening sight degradation (now affecting females). Yasuna's sight fully recovers, but she breaks up with Hazumu to "stand alone." The OVA concludes with Hazumu confessing to Tomari; they marry in a ceremony officiated by Hitoshi.

Hazumu's horticulture passion endures throughout, with gardening club activities remaining constant. Interactions with aliens Hitoshi Sora and Jan Pu (whose gynoid form mirrors Hazumu's new body) provide comic relief and explore themes of love and identity.