Misuzu, a timid human girl, finds her life disrupted when an alien claiming to be her older sister replaces her vanished sibling. Haunted by fragmented memories of her biological sister, she grapples with unresolved longing while navigating the alien’s obsessive fixation on “yurifying” the world. This enigmatic imposter drags Misuzu into surreal schemes, warping reality itself—transforming pollen to cure her hay fever with floral-themed particles or commandeering her timid younger brother, Ryōta, whose androgynous appearance invites the alien’s whimsical orders.

Her mother’s literary fascination with young girls and best friend Hii-chan’s unhinged infatuation—paired with a zeal for extraterrestrial lore—deepen the peculiar tapestry of Misuzu’s world. A robotic replica of the alien, lodged on the family roof, echoes her lost sister’s gentler demeanor, forcing Misuzu to oscillate between the imposter’s eccentric dominance and fleeting glimpses of familiarity. The alien’s possessive streak surfaces when it sabotages a rival robot’s attempt to comfort Misuzu, asserting control under the guise of protection.

Tasked with guarding Misuzu from a subway groper, the alien infiltrates her school life, masking world-domination agendas beneath layers of overbearing guardianship. Misuzu reacts with quiet bewilderment, oscillating between reluctant compliance and muted defiance, her observant nature anchoring the chaos. A pink-haired classmate pining for Ryōta and a yaoi-obsessed alien rival linger at the narrative’s edges, though Misuzu’s focus remains on reconciling the alien’s presence with her sister’s absence—a void left unresolved, her static role emphasizing endurance over transformation amid the absurdity.