Street Fighter Alpha

Gouken and Gouki both learned a very deadly form of karate from their master Goutetsu. This dangerous style can awaken the "Satsui no Hadou" in its practitioners. Gouken tried to remove these dangerous elements when he taught Ryu and Ken. But Gouki succumbed to the evil and killed Gouken. Years later, Ryu and Ken reunite at their master's grave. Ryu has secretly been showing signs of the Satsui no Hado. They are even more surprised when a boy named Shun shows up, claiming to be Ryu's long-lost brother! Then Shun also shows signs of the Satsui no Hadou. And Shun tells Ryu that their father also succumbed to the evil! A secret organization (Shadowlaw perhaps?) seeks to awaken this power in Ryu and harness it.