Chika, a young woman who had been planning to return to the workforce once her son entered kindergarten, sees those plans upended when her husband Tadashi is assigned to an overseas post. She gives up her own career to accompany him, arriving in a tropical southern country with dreams of a glamorous expatriate life. The reality is far different. Struggling to raise a child in a country where she does not speak the language, she finds her husband uncooperative and the local community of overseas spouses—known as chuzai-zuma—a source of unexpected stress. Instead of leisure and luxury, Chika is confronted with the disorienting isolation of life abroad and the pressure to fit in.

She soon becomes entangled with Emi, a wealthy and domineering senior spouse who offers friendship but quickly turns it into a relationship where Chika feels taken advantage of. At the same time, she meets Fumie, a local woman who is also an expat wife, and whose mysterious pregnancy becomes a source of tension and suspicion within the group. Chika, who sees herself as an ordinary middle-class wife, finds herself caught between these women and the hidden rivalries and secrets that simmer beneath the surface of their picture-perfect lives.

As the story unfolds, Chika's own marriage begins to fray. Tadashi repeatedly visits hostess bars without her knowledge, and despite a tense discussion where he seems to promise change, Chika discovers a business card from a nightclub in the laundry—proof that the betrayal has not stopped. The darkness in her home life deepens even as the expat community itself is shaken. Emi, who once ruled the group as the wife of the branch manager, becomes the target of a vicious and escalating campaign of bullying. With the shadow of a malicious senior colleague from the company, lies from her own husband, and the increasing attacks against Emi, the tensions in this seemingly idyllic tropical setting build toward an irreversible incident that changes everything for the women involved.