Chougen Yuuki: Mugenfinity

Eight years ago, the Voldan tried to invade the world, but were repelled by one man who risked his life for the future of the world. His name was Touma and he piloted a robot with the help of a young boy and a masked girl. After this incident, he left the world to fight other enemies. The young boy, Tamaki, was viewed as his successor, but he soon lost his powers with age. Now no one remembers him until he meets ‘him’ and ‘her’ and the story begins once again.

[From Hau~ Omochikaeri!]