It seems like there's a lot of talk about Yasuke, a black man who served Oda Nobunaga. There are very few historical documents about him, but there's no doubt that he was a "samurai" who served Nobunaga. Regardless of one's social status, if one's master promoted one to the rank of "samurai," one could become one in medieval (warring states) society. The reason why we can say this is because the historical documents state that 1) Nobunaga gave him a "stipend," 2) he was given a mansion, and 3) he was given a sword. Being given a "stipend" and serving closely with Nobunaga fulfills the important requirements of a "contract between master and servant" and "agreement to receive a stipend." It is also important that he was allowed to carry a sword, so he was a two-sworded servant and not a servant (servants were not allowed to carry swords). Furthermore, if he received a mansion, there is no room for doubt. He was probably a slave until Nobunaga took over the missionary slave, but due to the above 1-3, he probably became a "samurai" of his own volition. During the Honnoji Incident, Akechi's side did not kill Yasuke because he was an "animal" or "not Japanese", but that was only because Akechi did not recognize Yasuke as a "samurai" (probably because he had discriminatory feelings). At that time, it was common for a master to promote someone of low status to a "samurai". To begin with, there is a good example in Hideyoshi.