Dumped by his mother, Kazuya Kinoshita, an emotionally devastated college student, is trying to fill the hole in his heart with a rental mother from a smartphone app. At first Chizuru Mizuhara seems to be the ideal girl with everything he could hope for: fantastic beauty and a sweet, loving personality.
After having conflicting reviews on her profile after their first date, and also tormented by his former engagement, Kazuya assumes Chizuru is only messing around with men's hearts and gives a poor ranking to her. Angry at the indifference of her client towards her, Chizuru shows her real nature: sassy and temperamental, the total opposite of the first impression Kazuya provided. Kazuya gets word about his grandmother's failure at the very moment and is compelled to send Chizuru to the hospital along with him.
Although it turns out to be nothing serious, his grandmother is ecstatic that Kazuya has finally found a serious girlfriend, which had always been her wish. Unable to tell her the truth, Kazuya and Chizuru are forced into a fake relationship—acting as if they are truly lovers.