Sae Uchino is a thirty-year-old office worker who lives by a rigid sense of what is right. When her casual boyfriend abruptly dumps her by revealing they were never really dating, she spirals and seeks a paid date through a matching app. There she meets Tarou, a handsome, deliberately adorable young man who initially plays the part of the perfect pet. But when she lectures him about getting a real job, he drops the act entirely—revealing a crass, blunt, and lazy personality. Instead of walking away, Sae impulsively invites him to move in with her, rationalizing it as "keeping a pet."

The story unfolds as a strange romantic comedy of cohabitation. Tarou is a freeloader who does the bare minimum—occasionally cooking, lounging around—while Sae struggles with the ethical dissonance of "keeping" a person. Tarou, however, is no simple parasite. He was once a top salesperson whose career was destroyed by envious coworkers who doxxed and bullied him into quitting. His past trauma makes the domestic arrangement unexpectedly healing for both: Sae learns to loosen her grip on correctness, and Tarou finds a safe space where he can be himself without pretense.

The narrative is driven by the push-and-pull between Sae's upright nature and Tarou's manipulative yet oddly protective tendencies. A key arc involves the reappearance of Sae's ex-boyfriend, who tries to win her back, only to be rebuffed by Tarou's territorial claim. Tarou's own guarded feelings begin to surface, and Sae starts to see past his act. The manga balances humor and heart as each character confronts what they truly want—Tarou, whether he can stop being a parasite, and Sae, whether she can accept love that flouts her rules.