Ruka Hanari, a transfer student at Tsukinomiya Girls' High School, struggles with profound social awkwardness rooted in a traumatic incident: hesitating to aid a distressed girl in a flowerbed, only to later learn of the girl’s death, possibly by suicide. Haunted by guilt, she carries a photo of a similar flowerbed as her phone’s lock screen—a constant reminder of her perceived failure.

Her isolation fractures upon meeting Hiori Hirahara, an upbeat classmate who becomes her roommate. Their bond begins when Hiori climbs through their dorm window after curfew, sparking a shared vision of each other’s memories—an omen of their linked fates. Though initially resistant, Ruka slowly lowers her guard under Hiori’s persistent warmth, diligently studying self-help books on friendship to bridge the gap between her longing for connection and social anxieties.

Awakened as a Reflector during a crisis where Hiori sacrifices herself to shield her, Ruka wields a translucent straight sword and magic bow with agile precision. Her combat form—a two-toned blue dress adorned with pink accents, long boots, and gloves—contrasts her civilian sailor uniform and knee-length socks. This power marks her shift from reticent observer to determined protector.

Recurring failures, such as allies Ryoka and Amiru losing their Fragments to enemies, reignite Ruka’s guilt, yet fuel her resolve. During the final clash with antagonist Shino Mizusaki, she and Hiori shatter Shino’s shield together, cementing Ruka’s growth into an active force against conflict. Her journey peaks when she extends compassion to former foes like Shino, vowing to forge friendship despite their strife—a stark departure from her once-paralyzing self-doubt.

Though her family remains shrouded, her bonds with Hiori and Miyako Shirakaba anchor her emotional evolution, guiding her toward embracing vulnerability and mutual trust as strengths rather than weaknesses.