Cerberus

A normal high school boy Kisaragi Ryuji'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. In the box, they find a red dragon girl Rose. In order to protect Rose from the black organization, Ryuji decides to fight using his power as a relic handler.

The story revolves around "jushiki" (lit. spell equations), the equations that govern the quantum constant "h" of action, change the laws of physics at the local scale, give birth to TNT explosives and poison gas, and cause incredible physical phenomena such as plasma and nuclear fusion. Two "jushikishi" (spell equationists) who use jushiki in battle are Gayus (who deals with bad luck with tact) and the beautiful but cruel sword-wielder Gigina. These two bounty hunters are caught up in a battle with dragons in the city of Eridana and in the intrigue of great nations.

The story of a young girl and a young dragon. Naturally, they are the best of friends, and naturally the rest of the world is against them both. However, when demons decide to trash their world, they side with those who have always been against them.

The story takes place in the sparkling era year 3015, where the great nations Donatia and Kouran divide the world in a cold war as they fight for supremacy. In the middle of this standoff is island country Nil Kamui, which has lost its independence.