Akari Yamamoto, a high school student with a pragmatic outlook on romance, contrasts sharply with her idealistic friend Yuna Ichihara. Raised by a single mother in a transient lifestyle marked by repeated school changes, Akari’s stability shifts when her mother marries into the Yamamoto family, granting her Rio Yamamoto as a stepsibling. Their familial tensions stem from her mother’s distrust of Akari’s bond with Rio, complicated by his concealed romantic feelings—a reality Akari has deliberately overlooked since its inception.

Her romantic history weaves fleeting relationships with an unresolved childhood attachment to an older neighbor, symbolized by a kept bracelet he discarded. Relocating near Yuna, Akari forms a friendship that draws her into Yuna’s circle, including childhood companion Kazuomi Inui. Though initially scheming to pair Yuna with Inui, she halts upon discerning Yuna’s affection for Rio. Gradually, Akari’s calculated approach to love unravels as genuine feelings for Inui emerge, tested by his initial rejection to shield Rio, lingering ex-boyfriend conflicts, and her own emotional defenses.

Yuna’s forthrightness challenges Akari’s guarded persona, catalyzing growth rooted in her fractured family history—an absent father, Derek Yamamoto, and a mother’s pattern of unstable marriages. Forced into self-reliance, Akari masks vulnerability until gradual openness reshapes her relationships. The narrative concludes with her reconciling with Rio through Yuna’s intervention, then relocating to America with her parents. There, she awaits Inui, who eventually follows to chase his ambitions.

Akari’s name, blending "vermilion red" (朱) and "village" (里) with her surname’s "mountain" (山) and "origin" (本), mirrors her journey from self-protective isolation to embracing connection. Her arc traces emotional maturation, familial healing, and the struggle between guarded independence and the risks of authentic intimacy.