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