I guess it's Yasuke. The guy existed, it's totally documented. Arrived with a Portuguese Jesuit mission as a servant, probably a bodyguard since apparently after being sold as a child, Yasuke had ended up in India and had been a soldier. Nobunaga liked found him exotic and thought he must be strong, so he decided to keep him as a retainer and it's documented that he was armed and was kept in Nobunaga's inner circle and even fought alongside him and was there when he died. All evidence though indicated that he was NOT a samurai in the social caste sense, armed warrior or not.

The issue then, is not that Ubisoft chose the character of Yasuke -- but the role they make him play. If I understand the trailer correctly, the female character follows the usual AC plot line and is against the centralization of power and unification of Japan, so her foe in this case should likely be Nobunaga? And Yasuke, who was historically documented to be a loyal Nobunaga warrior goes and allies with her?

I will need some clarification about this, since Ubisoft insists so much that all they do is based first of all in historical research...