In a ancient empire, a tactician who is known as Rui Kamishiro work with the emperor of the empire. He have been working as a tactician for 4 years. Rui also have a secret and that is, he have an ancient dragon god hidden in his chambers, keeping the dragon save from danger. The dragon's name is Tsukasa Tenma. They both are also dating.

One night, Rui just got back from work and into his chambers, Rui saw a familiar dragon tail sticking out from underneath a blanket in the living room.