A normal high school boy Ryūji Kisaragi’s peaceful life is turned into an adventure by the return of his second cousin, Eriko. Ryūji and Eriko seize a relic box from a black market broker named FANG. In the box, they find a red dragon girl whom Ryūji names Rose because of her rose like pattern on her left hand. In order to protect Rose from the black organization, Ryūji decides to fight using his power as a breaker.