Tsukasa Tenma is the prince and heir to the throne of the Light Kingdom. His father always placed great hopes on him, which was sometimes difficult. He had long had his own personal butler, Rui, and rumor has it that he is from the Dark Kingdom. There was a war. It took the person most precious to the prince—his younger sister. And he also lost his sight completely. The more time passed, the more the prince's light faded, no matter how hard he tried.