Once upon a time, the world had been divided into the Moon Kingdom, inhabited by humans, and the Sun Kingdom, inhabited by demons. Estelle, a knight of the Moon Kingdom, loses her family to an ambush from the demons and is sentenced to life in exile after becoming entangled with a mysterious demon child. To survive, she sets out to a mysterious tower in the north with her companions. A timid knight, a slave boy, and a shadow who was once the Demon King.

This is an alluring story about three people embarking on an adventure to find their true selves.