Shinobu Miyake begins as the childhood friend and girlfriend of Ataru Moroboshi, their relationship destabilizing when Lum, an alien princess, mistakenly believes Ataru has proposed to her. Prior to Lum’s arrival, Shinobu vowed to marry Ataru if he defeated Lum in a high-stakes game of tag—a promise meant to spur his determination. Yet Ataru’s victory celebration is misread by Lum as a proposal, triggering Shinobu’s growing disillusionment.

Petite with short brown hair and clad in a sailor-style school uniform, Shinobu exudes gentleness and patience, masking latent superhuman strength that erupts during intense anger or frustration—often provoked by Ataru’s flirtatious antics or perceived betrayals. Her ability to hurl heavy objects, like school desks, serves as a comedic hallmark, fueled by jealousy toward Lum. This power wanes in contexts devoid of Lum’s influence, as seen in one film where her rage no longer ignites the same force.

Estranged from Ataru, Shinobu redirects her affections toward Shūtarō Mendō, a wealthy classmate. Though mutually attracted, their potential bond falters due to Mendō’s fixation on Lum and flaws paralleling Ataru’s, trapping Shinobu in a pattern of unreciprocated longing.

Her trajectory shifts upon meeting Inaba, an agent of the Destiny Production Management Bureau. Collaborating to retrieve a flower from a space-time forest, they bond as Inaba prioritizes time with Shinobu over mission objectives, sparking mutual affection. This relationship culminates in a stable, reciprocated romance by the narrative’s end.

Beyond romance, Shinobu’s initial animosity toward Lum mellows into camaraderie as she distances from Ataru. She also supports peers like Ryūnosuke Fujinami, urging Ryūnosuke to embrace femininity despite being raised as a male heir.

Thematically rooted in endurance—reflected in her name’s meaning, “endure”—Shinobu weathers repeated heartbreaks and supernatural trials. Her resilience ultimately finds fulfillment through Inaba, resolving her protracted struggles.