That is Pollux rui Britannia
Pollux rui Britannia is a character exclusive to the Nintendo DS video game and a member of the Britannian Imperial Family. He pilots the Knightmare Frame Aquila. Pollux possesses the same Geass ability as Lelouch, though when brought against one another his seems to be inferior. His twin brother is Castor rui Britannia and pilots the Knightmare Frame Equus. Castor possesses a Geass that allows him to telepathically communicate with his twin brother Pollux. He is frequently mistaken for his brother, much to his annoyance. Both he and his brother are likely named after the Greek and Roman mythological twin brothers, Castor and Pollux, respectively.
You have to fight them in a other route.
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