Paprika, an American exchange student living in Japan with her best friend Juicy, shares a childhood history with her cousin Chibiham in the United States. Paprika recalls Chibiham habitually wearing stained t-shirts and consuming excessive sugary snacks during family reunions. Their relationship showed strain at age fourteen when Chibiham reacted negatively to Paprika's anime purchases during a mall visit.

Inviting Chibiham for a month-long homestay in Japan after years apart, Paprika meets her cousin at Haneda Airport alongside Juicy, though with noticeable reluctance. Acting as Chibiham's host and cultural mediator, Paprika faces mounting frustration over her cousin's entitled behavior. This includes public disturbances, refusing Japanese cuisine, and disrespecting local customs—specifically declining a train seat to an elderly person, rejecting Juicy's homemade meals, and causing a scene in a Harajuku store by handling merchandise with chocolate-covered hands. Paprika repeatedly resolves these conflicts and cleans physical messes, including bathroom accidents stemming from Chibiham's unfamiliarity with Japanese toilets.

Juicy's mother joins their outings, where Chibiham continues complaining about the food. Paprika witnesses the pivotal moment when Juicy's mother confronts Chibiham's closed-mindedness, leading Chibiham to reluctantly try sushi and acknowledge its taste. While this marks a subtle shift in the dynamic, Paprika remains primarily reactive to her cousin's behavior throughout the visit.