“ Yeah, exactly how many black Africans were in Japan at the time?”
It’s quite likely the Portuguese had African slaves on their ships and as laborers in their colonies and outposts, but I’m not sure if any made it to Japan. However, since this is fiction, I won’t be surprised if somebody sues the writers for some DEI slight.
There’s a thesis topic for your Ph.D. in Afro-American Studies. You’d probably get a full-ride scholarship to cover that one.
There were a few, and one who became famous, but with Japan we're at the point where we were with medieval England 20 years ago. Working Black characters into the show for DEI would just look ridiculous and stupid.
Another interesting thing: for a while the Portuguese navigators were enslaving Chinese and Japanese and taking them back to Portugal and the colonies. The Japanese rulers didn't like it and made them stop.