The Princess of the Moon Country, Trivia, was under house arrest in the castle.One day, taking advantage of the commotion of the festival, she escapes from the castle and meets a boy with mysterious eyes."When I grow up, let's travel the world with me."Having made a promise to him that she hit it off, Trivia returned to her usual cramped life, keeping her promise to herself. ――8 years later. She grew up in her splendor,She planned to leave the next day after completing her coming-of-age ceremony.In order to fulfill a promise she made to him she met a long time ago.However, a tragedy strikes her.This is a princess story that begins with one "promise".