https://en.m.wikipedia.org/wiki/Yasuke
More info here.
Looks like there was a black samurai.
Discussion
Not a samurai. A warrior at Nobunaga's service and a loyal one apparently. Doesn't mean he was made part of the samurai class. For instance, he was not made commit seppuku after Nobunaga's death, unlike all his surviving samurai allies.
If he had any honor he would have joined the other allies.
Seems like he had a hand in it.
That would in fact make a good plot for the game, as speculation.
I am thinking now, Yasuke came with and went back to the Jesuits. And weren't the Jesuits the antagonists in the AC series?
This made up Yasuke who allies with Nobunaga's enemies is even more inconsistent than it looked at first.