Kazuya Kinoshita is a 20-year-old college student who is dating the bright and cheerful Mami Nanami, a wonderful girlfriend. But suddenly, without warning, Mami breaks up with him, leaving him utterly heartbroken and lonely. Trying to ease the pain, he hires a rental girlfriend through an online app. His date is Chizuru Mizuhara, whose unparalleled beauty and cute demeanor win over Kazuya's affection.
However, after reading about other customers' similar experiences with Chizuru, Kazuya becomes convinced that her warm smile and caring personality were just an act meant to toy with his heart, so he gives her a low rating. Angered, Chizuru lashes out at him for his shameless hypocrisy, revealing her true blunt and fiery nature. This one-sided argument is cut short when Kazuya learns that his grandmother has collapsed.
They rush to the hospital and find that Kazuya's grandmother is already in good condition. Baffled by Chizuru's presence, she asks who this girl is. On impulse, Kazuya instantly declares that they are lovers, forcing Chizuru to play along. But with Kazuya still hung up on his past relationship with Mami, how long can this difficult client and reluctant rental girlfriend keep up the charade?