Legend of the Dragon Kings Souryuuden

The four Ryudo brothers hold an ancient secret – they are descended from the dragons. They have the speed, strength and power of their legendary ancestors – and they’re getting stronger. But when pushed to the limit, they become the terrifying, uncontrollable dragons of mythology. These powers have attracted the attention of some powerful enemies – shadowy organizations with unlimited resources and weapons who will stop at nothing to control the brothers.

(Source: U.S. Manga)