Strider Hiryu

The manga is set in the year 2048 and centers around Hiryu, a young Super A-grade Strider who retired early during his career after he was forced to kill his elder sister Mariya, a Strider who went insane (as shown in the prequel story). The main series begins with Hiryu living peacefully in Mongolia when his former superior, Vice Director Matic, forces him out of retirement in order to kill his best friend Cain, who has been captured by hostiles in the Kazakh SSR and has become a liability to the rest of the Striders.