The overhead continent "Oseland" is divided into the "Eternal Day Kingdom" (which believes in the sun goddess and masters light magic) and the "Eternal Night Empire" (which serves the moon god and is proficient in dark magic). For thousands of years, they have fought endlessly for the ownership of the "power of the star track" - it is said that the "Star Altar" in the center of the continent gathers the energy of the star track every hundred years and can realize a wish of the holder, and the energy core "star core" needs to be activated by the "twin bloodlines of light and darkness". The story begins with a change in the Star Altar. The male protagonist (Eternal Day Knight) and the female protagonist (Eternal Night Witch) are bound to a "soul contract" due to an accident. While fighting against the crisis on the continent, they reveal the ancient truth about the "symbiotic symbiosis" between the light and dark races.
