"Rent-A-(Really Shy!)-Girlfriend" centers on Kazuya Kinoshita, a college student who, after being dumped by his girlfriend, turns to a rental girlfriend service to cope with his loneliness. Through the service, he meets Chizuru Mizuhara, a seemingly perfect and composed rental girlfriend. Initially, Kazuya is unimpressed, but after a series of events, he begins to see her genuine personality, which contrasts with her professional demeanor. Chizuru is ambitious, hardworking, and harbors dreams of becoming an actress, though she struggles with her own insecurities and the pressure to maintain her rental girlfriend persona.

As the story progresses, Kazuya and Chizuru’s relationship becomes increasingly complicated. Their interactions extend beyond the rental arrangement, leading to a mix of comedic and dramatic situations. Kazuya’s family becomes involved when his grandmother falls ill, and he impulsively introduces Chizuru as his real girlfriend to avoid disappointing her. This lie spirals into a web of deception, as both Kazuya and Chizuru must navigate their fabricated relationship while dealing with their growing feelings for each other.

The narrative explores themes of self-discovery, emotional vulnerability, and the complexities of modern relationships. Supporting characters, such as Ruka Sarashina, a persistent and emotionally driven rental girlfriend, and Mami Nanami, Kazuya’s ex-girlfriend who re-enters his life with unclear motives, add further layers of tension and conflict. The story balances humor, romance, and introspection, delving into the characters’ personal struggles and the blurred lines between professional and personal connections. Through its episodic structure, the series examines the challenges of communication, trust, and authenticity in relationships, while maintaining a focus on the evolving dynamic between Kazuya and Chizuru.