Seven years ago, a young girl named Tama-tan met a mysterious boy with rabbit ears who gave her a small pendant and made her promise to wait for him. She has held onto that memory ever since, but as time passes, she begins to doubt if the encounter was real. That doubt vanishes when a flying saucer suddenly appears before her, and the boy from her past finally returns. He is Mitsuaki, the prince of the Moon, and he has come to Earth on an urgent mission to find the Lunar Ladies—candidates who can become the Moon Princess.

The story follows Tama-tan, a cheerful, hyperactive, and surprisingly frugal elementary school girl whose full name is Nishikiori Tamae. Her life becomes far more complicated when she learns that both Earth and the Moon are in danger, and that the key to saving both worlds is the selection of a new Moon Princess. Much to her own surprise, Tama-tan is chosen as one of the candidates. She joins several other girls at her school who are also Lunar Lady candidates, including her good friends Shiki, a ninja clan heir with a boyish personality, and Mii, a gentle and popular former idol. However, not all candidates are friendly; the haughty and competitive Miharu, a descendant of an angel, sees Tama-tan and her friends as her primary rivals.

As Tama-tan navigates her new reality, she discovers that she has a natural talent for love magic. She also finds her feelings for the quiet and reserved Prince Mitsuaki growing stronger, complicated by a childhood promise that some consider a secret engagement. The group faces interference from Mitsuakis older brother, Kai, whose black rabbit ears cost him his right to the throne. Bitter and seeking revenge, Kai schemes against Mitsuaki and develops a strange obsession with Tama-tan, first after being hit by her love magic and later as part of his plans to use her for his own purposes.

The narrative arc focuses on Tama-tans journey from a seemingly ordinary girl into a powerful Lunar Lady. She must overcome her own doubts and failures during the princess trials to unlock her true potential. The story weaves together daily school life and magical battles, exploring themes of friendship and first love. It also serves as a spin-off to the manga Kamichama Karin, with Tama-tan later revealed to be the daughter of Michiru Nishikiori, a character from that series.