Subaru is one of the Steel Saints Mitsumasa Kido's technologically enhanced special backup unit for Athena's Saints, created decades ago.

One day, after learning about Pegasus Koga and his deeds, climbing the Twelve Temples and defeating both Mars and Abzu to be specific, he appeared at a Steel Saint training facility. He trained harder than anyone, never speaking to anyone, until one day he met Erna, another Steel Saint. He spoke to his new friend, declaring his intention to become like Koga, and to defeat him.

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 Kouga, 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 Kouga awakens to the power of his Cosmo hidden inside him, the curtain will rise upon the legend of a new Saint.
 
(Source: Anime News Network)

Bruno Abundis Coronel is a voice actor from Mexico.

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 Kouga, 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 Kouga awakens to the power of his Cosmo hidden inside him, the curtain will rise upon the legend of a new Saint.

Subaru Equuleus