In modern-day Tokyo, a rental agency exists where people down on their luck can hire companions, including fake girlfriends for a day. Kazuya Kinoshita, a 20-year-old college student, is reeling after being dumped by his girlfriend Mami Nanami after just one month of dating. Feeling desperate and lonely, he uses an app to rent a girlfriend and is matched with Chizuru Mizuhara, a stunningly beautiful young woman who seems perfect on the surface—polite, attentive, and impossibly sweet.

Their first date goes smoothly, but Kazuya suspects her perfect demeanor is just an act. He leaves a harsh one-star review, which leads to an explosive confrontation when they meet again. Chizuru drops the sweet act and berates him for his rudeness, revealing her true, more temperamental and sharp-tongued personality. Before they can part ways, Kazuya receives word that his beloved grandmother Nagomi has collapsed and is in the hospital. Unable to explain the rental arrangement, he brings Chizuru along, where his grandmother instantly adores her and is overjoyed that her grandson has finally found a serious girlfriend.

To maintain the charade and keep his family happy, Kazuya is forced to continue renting Chizuru. The situation quickly becomes impossibly complicated when he discovers that Chizuru is not only his next-door neighbor in their apartment complex but also a fellow student at the same college, where she goes by her real name, Chizuru Ichinose, and hides her beauty with glasses and braided pigtails. The fake relationship becomes a tightly-woven secret that dominates both of their daily lives.

As Kazuya continues to hire Chizuru, his ex-girlfriend Mami re-enters the picture. While she appears sweet and friendly on the surface, she harbors jealous and possessive feelings, and she becomes suspicious that Kazuya found someone new so quickly after she dumped him. Complicating matters further, more girls from the rental girlfriend world begin to intrude on his life. Ruka Sarashina, a girl with pink hair and a shy personality, is a newcomer to the rental industry who develops real feelings for Kazuya after he helps her improve her dating skills. She has a health condition involving a low heart rate, and Kazuya is the first boy who makes her heart beat faster naturally. Another rental girlfriend, Sumi Sakurasawa, is a shy girl who also works for a different agency and finds herself drawn to Kazuya's kind and passionate nature.

Throughout the series, Kazuya works part-time at a karaoke bar to afford the expensive rental dates while trying to sort out his increasingly messy romantic life. As time passes, his feelings for Chizuru grow from simple infatuation into genuine love. He learns that Chizuru has a deep-seated dream of becoming an actress, a passion inherited from her late grandmother Sayuri, who was a performer in her youth. Chizuru lost her single mother at a young age and was raised by her grandparents; the loss of her grandfather and the failing health of her grandmother weigh heavily on her. Determined to move their fake relationship into reality, Kazuya becomes dedicated to supporting Chizuru’s dream, leading to a major narrative arc where they work together to crowdfund and produce an independent film to help her pursue her acting career and grant her dying grandmother's wish to see her perform.