Takashiro Giou

Takashiro is first introduced as Yuki's older half-brother. When he meets Yuki for the first time, he tells him that he and his father had been looking for him ever since his birth fifteen years earlier. He is also the head of the Giou clan. Although it is not yet revealed, Takashiro seems to be hiding something from Yuki and the rest of the Guardians. The truth is he preformed a forbidden ritual that allowed him to take a dura into his body. Because of this he, unlike the other Zweilt Guardians, has not been reincarnated. Instead he has lived for a thousand years, remembering everything, including how the war with duras first began. He also heals almost immediately after being injured. He believes that in order to win the war, there have to be sacrifices. He possesses a magic book much like Kanata, although his is red. It has been told that Reiga was his friend. He is shown during a battle with Reiga to be able to regenerate himself without any help, and reveals to Yuki later that he used a forbidden spell on himself that put a duras inside his body, which is how he was able to heal, and that because of that duras, he is immortal and has lived over 1000 years. He is also the one responsible for continually causing Yuki and the Zwielt to reincarnate so they can continue fighting Reiga. He then apologizes for lying to Yuki, telling him that he is not really Yuki's brother, but Yuki forgives him, telling him that despite that, Takashiro is still very important to him.

(Source: Wikipedia)