Everywhere you read about that "Black Samurai" that rose from slavery to aristocracy in Japan thanks to the sense of Justice of Nobunaga, but things were quite different in reality.
The "boom" about Yasuke was introduced by a documentary of sort aired on the Japanese TV on 2013 and keen on explaining the mysteries of the world. After studying the raw materials, the conclusion of the investigation stated that Yasuke was a Makua whose real name was Yasufe.
I made the effort to check the references provided by the documentary to see how fitting was the result.
First of all, I checked the report on the subject by our first source, that François Solier who documented the Japanese missions in his "Histoire Ecclesiastique Des Isles Et Royaumes Du Japon".
Here's a translation from French provided by my kind friend Hervè:
"The day of Easter was celebrated in great devotion. After the feast, Father Alexandre went to Meaco to see Nobunaga and thank him for the favors that he continuously bestowed upon Christianity and to our fathers who were preaching in his kingdoms. However Father Alexandre had brought with him from the Indies a Mozambican valet as black as those Ethiopians from Guinea. This cafre was one of those inhabitant from Cape of Good Hope. Suddenly as soon as he arrived here, all the town inhabitants came to see him. Father Organtin brought him to Nobunanga who received him greatly and couldn't believe this skin colour was natural and believed he had been painted for fun."
Father Alexander, or the guy that later on Frois would call "Father Visitor", was Alessandro Valignano, one of the supervisors of Asian missions with a soft spot for Japan.
"Cafre" is the portuguesization of the Arabian "Kaffir", or "Unbeliever", the insult that at the beginning described the non-Muslims, but later on would applied to black guys indiscriminately-- It must be noted thought, that during the times of Solier, "Cafre" was not meant as an insult, but it was just used to descrive those Africans sold on the slave markets by Arabians.
So, the origin of Yasuke was definitely that of a slave: even if Jesuits themselves opposed to the market of slaves and slavery, still made use of "servants"; that word, valet that I left in French, means "servant" or "attendant" rather than "slave"... So please take off from your mind the plantations of sugar in South-America and those of cotton in North-America.
The same event is told by Luis Frois in his Cartes; here's my translation from Italian, from the letter sent to Lorenço Mexia on 1581:
"That same Sunday, we left for Vocasama, and outside there were people waiting, impressed by the height of our Father and the darkness of our Moor.[...] On Monday there was so many persons in our home, coming to see our little Moor, that there were some troubles. Knowing this, Nobunaga ordered to bring him to him, and Father Organtino did so. Nobunaga laughed happily when he saw him, and had him getting naked from head to belt, thinking that the colour of his skin wasn't real, but a trick. Even his sons and his nephew wanted to see him, entertained: the nephew, a captain of Osaka, presented him 10.000 caxas."From this piece we can tell that Nobunaga didn't call Organtino and the "little Moor" only because he was curious about him, but also to get a report about the turmoil happening around the church, getting distracted by the sensation meanwhile.
Nobusumi didn't give Yasuke "10.000 caxas" because he wanted to gave him a mean for living, it was rather a tip for the fun experience.
Also, the thing about Yasuke being around 2 meters tall, is probably a mistraduction: both Nobunaga and the people were impressed by the height of Father Valignano, not Yasuke's, who was a young man, if not a boy (as the "little Moor" implies).
Also, I read everywhere that Nobunaga demanded for him to bath to make sure of Yasuke's dark skin, and even about retainers scrubbing him: I didn't find anything on the reports about this.
Last, here's the contribution of Ota in his "Shichoukoki":
"On the 23rd of the Second Month, a blackamoor came from the Kirishitan country. He appeared to be twenty-six or twenty-seven years old. Black over his whole body, just like an ox, this man looked robust and had a good demeanor. What is more, his formidable strenght surpassed that of ten men. The Bateren brought him along by way of paying their respects to Nobunaga."The original word used by Ota for the "blackamoor" of Lamers was "黒坊主" which means "a black-skinned priest", which means that he was probably introduced, or perceived, as a fellow missionary rather than a mere servant... If anything, I doubt that he was a fellow Jesuit, as previous education and official confirmation from the Roman Church was needed for that, but Yasuke definitely felt like more of an attendant rather than a mere slave, expecially because Frois used very affectionate terms to describe him.
Ota also mentions that this "black priest" had a good demeanor, and some other unknown sources stated that he could talk with Nobunaga, and assuming that he could speak a decent Japanese, he was given proper education.
This said, it's pretty improbable that "Yasuke" was a "japanization" of his "true name". The boy was definitely baptized if he was allowed to follow around Valignano, so his name was Western, and not something exotic as Yasufe.
It's also difficult to imagine that Nobunaga would grant him the use of his true name once in his service, as it was a custom to rename retainers and servants alike, expecially if they were foreigners... Think of William Adams, the first Western Samurai, who was properly renamed Miura Anjin: it sounded (and meant) nothing as his original name, and he was an actual daimyo, on the contrary of Yasuke.
This said, the first source that came up with the name "Yasuke" was a children book of 1968 which artworks by Minoda Genjirô decorate this article, "Kurosuke" by Yoshio Kuruso.
Here it's mentioned that this black guy was given the name "Yasuke Karusan" by Nobunaga, but everyone nicknamed him "Kurosuke" because of his dark skin, which explains the title of the book.
So, if anything, even the name "Yasuke" is a mere fabrication.
Anyway, after these proofs, nothing is left to know about Yasuke and his whereabouts.
It's only in the Cartas dating 1585 that we got more informations about him, during Frois report about the fall of Nobunaga on 1582:
"After all of this, only one doubt was left to us, that a Moor coming from the Cape of Good Hope, left by the Father Visitor to Nobunaga, after the death of his lord, went to the house of the Prince and here he fought furiously so that a servant of Acheci asked for his surrending, with the promise of no harm: after he surrended his sword, the servant asked Acheci what to do with the black one, and he answered; this Moor is a beast, he does nothing and he's not Japanese, so don't kill him, but give him back to the temple of the Fathers from India. Thus our men were relieved, grateful to the mercy of our lord."Now, this piece was generally interpreted as Yasuke being spared by Akechi but getting missing.
It's probably me forcing on some optimism into the whole story, but it felt to me that it's proof that Yasuke got back to the Jesuits after his fight at Nijo castle as a last attempt to save at least Nobutada. Why, you ask? Well, because that description of the events and the words that Akechi spoke were things that only Yasuke could tell to the Jesuits, and the source of the relief of the guys!
Even so, searching about this mysterious man gave us more questions rather than answers, contributing to the legend around this black guy going by the name of "Yasuke"...