Satomura Akane is a reserved high school student with long blonde twin braids and green eyes. She consistently wears a sailor uniform with a ribbon tie and carries a distinctive pink umbrella on rainy days. Her antisocial, kuudere personality manifests through emotional distance and minimal speech, often rejecting others' help with a blunt "no"—especially when offered by classmate Kohei Orihara.

Akane's past revolves around a childhood trauma: her beloved friend Tsukasa vanished into the Eternal World, a mystical dimension within an empty lot near their school. She now waits there on rainy days with her pink umbrella, clinging to his promise of return. This event left her withdrawn, isolating her from peers except childhood friend Shiiko Yuzuki, who attends another school. Shiiko alone receives Akane's openness, despite having forgotten Tsukasa entirely.

Akane excels at cooking her own lunches and harbors a pronounced sweet tooth. During breaks, she crafts a self-designed picture book, channeling her introspection. Her narrative unfolds as Kohei uncovers her past and ties to the Eternal World. Facing his own disappearance into that realm, Kohei’s plight mirrors her vigil for Tsukasa. Akane lowers her emotional barriers, shifting from aloofness to reliance on Kohei. When he vanishes, she chooses to wait for him as she did for Tsukasa.

Her arc concludes with this enduring vigil, transitioning her isolation into quiet, resilient loyalty.