Chinpui follows the story of Eri Kasuga, a normal, somewhat lazy schoolgirl whose life is turned upside down when a small, mouse-like alien named Chinpui arrives from the planet Mahl. Chinpui informs Eri that she has been chosen to be the bride of Prince Lululu, the heir to the Mahl throne. Despite her initial refusal and desire for a normal life, Eri is constantly pestered by Chinpui and his magical gadgets, which he uses to try and convince her to accept the proposal. The series focuses on the comedic interactions between Eri, Chinpui, and her friend Uchiki, as they navigate the absurd situations caused by Mahl's advanced technology and the pressure of the impending royal marriage. While Chinpui attempts to win Eri over with wonders and promises of luxury, Eri remains skeptical, leading to a lighthearted exploration of friendship, growing up, and the clash between ordinary human life and extraterrestrial expectations.