Kozue is a high school student whose profound passion for astronomy drives her regular stargazing and led her to found her school's astronomy club. Her fascination with the stars ignited after receiving a metallic fragment from a fallen meteorite, which she wears on her wrist; this object deepened her interest in celestial phenomena and cemented her aspiration to work in a planetarium. Though other club members lack her fervor, her dedication persists.

She radiates an optimistic and cheerful personality, unconstrained by convention. Kozue harbors a persistent sense of an unknown voice calling her, compelling her to undertake a solo journey during summer break to view a meteorite and seek its source. This internal pull underscores her determination to independently pursue personal quests.

On her trip, she encounters a boy named Ginga at an old planetarium. Kozue is immediately struck by his lonely, sad eyes and feels drawn to him. Despite Ginga's reserved, distant demeanor and his obligation to wear a protective suit during scientific missions, she actively strives to connect with him. Her persistent efforts to bridge their communication gap gradually break through his emotional barriers.

Kozue becomes pivotal to Ginga's development, encouraging him to assert autonomy over a life largely controlled by scientists exploiting his abilities. Through their shared experiences, she inspires him to make independent choices, culminating in a transformative moment under the starry sky. This journey highlights her empathetic nature and her influence in fostering personal growth in others.