After being dumped by his first girlfriend Mami Nanami following a month-long relationship, college student Kazuya Kinoshita finds himself in a state of loneliness and desperation. On an impulse, he turns to a smartphone app that offers a rental girlfriend service, where clients pay by the hour for a companion to accompany them on dates. He goes on a date with Chizuru Mizuhara, a stunningly beautiful and poised young woman who acts like the perfect girlfriend. Dissatisfied with the artificial nature of the experience, Kazuya confronts her, leading to Chizuru dropping her professional facade and revealing a more fiery and authentic personality. A series of extraordinary coincidences soon forces them back together when they discover they are neighbors in the same apartment complex and also attend the same college.

The situation escalates when Kazuya’s grandmother is hospitalized. During a visit with Chizuru, both of their grandmothers recognize each other as friends. To avoid disappointing his family, Kazuya impulsively claims Chizuru is his real girlfriend. Chizuru, whose real name is Chizuru Ichinose and who dreams of becoming an actress, reluctantly agrees to maintain the facade to honor her own grandmother’s wishes. They agree to continue this fake relationship, a decision that entangles them in a complex web of lies involving their families, friends, and classmates.

The story is set in contemporary Tokyo, primarily around the fictional Nerima University campus, the characters’ apartment buildings, and various city locations such as karaoke bars, beaches, and hot springs resorts. As the series progresses, additional characters enter the situation, further complicating the central lie. Ruka Sarashina, a rental girlfriend with a heart condition that makes her heart beat slowly, discovers the secret and, after finding that Kazuya makes her pulse race, aggressively declares herself his provisional girlfriend. Sumi Sakurasawa is a painfully shy junior rental colleague who goes on practice dates with Kazuya to overcome her anxiety. Meanwhile, Kazuya’s ex-girlfriend Mami re-enters the picture, appearing sweet on the surface but harboring dark and jealous tendencies as she observes Kazuya’s new relationship.

Notable narrative arcs throughout the series include a trip to a beach resort where Mami attempts to sabotage the fake couple, a hot springs vacation where their grandmothers intentionally leave them in the same room, and Kazuya’s growing realization of his genuine romantic feelings for Chizuru. A significant arc in later seasons focuses on Kazuya’s efforts to support Chizuru’s acting career. After learning that her grandmother’s greatest wish is to see her perform on stage, Kazuya takes the initiative to organize a crowdfunding campaign to produce an independent film starring Chizuru. This project forces him to move beyond his usual insecurities and demonstrates his deep commitment to her, even as their relationship remains officially a client-renter arrangement.