A world divided in two, the 'Lunar Kingdom' where humans live and the 'Sun Kingdom' where demons live. Estelle, a knight of the Moon Kingdom, loses her family in an attack by demon tribes, gets involved with a strange demon tribe girl, and is sentenced to a life sentence. Live To do so, you must go to the northern tower. A timid girl-knight, a slave boy, and a demon king who became a ghost. The story of three people who embark on an adventure to find their lives.