One glaring thing i noticed that people have missed is that Yasuke had no last name (family name). In ancient times, Japanese peasants didn't have last names only the nobility and the samurai did. So the fact that Yasuke has no last name/family name and was never given one means he was never accepted as a samurai. (besides the fact that you know....the title of samurai was passed down through blood and you couldn't just become one anyways)
Of course this is just if Yasuke did exist, but he didn't.
The first thing I thought when I heard about Yasu (which was like last week; I'm not a weeb) was that bringing blacks to Japan is exactly the kind of thing Jesuits would do. Those guys brought blacks everywhere, often in chains. And I had been watching the first few episodes of "Shogun" so I was thinking about Jesuits and the Portuguese.
But yeah Jesuits and black/slavery is a pretty good google search. They're still apologizing for it.