Saint Seiya Omega

The god of war and guardian of his namesake planet, Mars, was once sealed away by Seiya, but time has passed and his revival is at hand. Meanwhile, Saori Kido (Athena) is raising the boy Kōga, whose life Seiya saved, and he's been training every day to become a Saint in order to prepare for the coming crisis... Unaware of his destiny, when Kōga awakens to the power of his Cosmo hidden inside him, the curtain will rise upon the legend of a new Saint.

Synopsis from Anime News Network