Much of what is known about him is found in fragmentary accounts in the letters of the Jesuit missionary Luís Fróis, Ōta Gyūichi's Shinchō Kōki (信長公記, Nobunaga Official Chronicle), Matsudaira Ietada's Matsudaira Ietada Nikki (松平家忠日記, Matsudaira Ietada Diary), Jean Crasset's Histoire de l'église du Japon and François Solier's Histoire Ecclesiastique des Isles et Royaumes du Japon.

[13] Based on Ōta Gyūichi's biography of Nobunaga, Shinchō Kōki, Yasuke was estimated to be in his mid-twenties in 1581.

[1] Researcher Thomas Lockley has also proposed that Yasuke might have originated from the Dinka people of what is now South Sudan.

[20][21] On 27 March 1581, Valignano, together with Luís Fróis, who had arrived in Japan earlier, had an audience with Nobunaga, and Yasuke is said to have accompanied them as an attendant.

[22][6] Luís Fróis's Annual Report on Japan states that Nobunaga also longed to see a black man, and summoned him.

Organtino took Yasuke to Nobunaga, who upon seeing a black man for the first time, refused to believe that his skin color was natural and not applied later, and made him remove his clothes from the belt upwards.

Indeed, it was owing to Nobunaga's power and his glory that yet unheard-of treasures from the Three Countries and curiosities of this kind came to be seen here time and again, a blessing indeed.

[6] He gave him the Japanese name Yasuke,[b] accepted him as attendant at his side and made him the first recorded foreigner to receive the rank of samurai.

[1] Nobunaga granted Yasuke the honor of being his weapon-bearer and served as some sort of bodyguard[29][30] According to Lopez-Vera, he was occasionally allowed to share meals with the warlord, a privilege extended to few other vassals.

[30] The Shinchō Kōki of the Sonkeikaku Bunko (尊経閣文庫) archives states: It was ordered that the young black man be given a stipend (扶持, fuchi), named Yasuke, and provided with a sword (さや巻, sayamaki),[c] and a private residence.

[9][10] The description of 11 May 1582 states: Nobunaga-sama was accompanied by a black man who was presented to him by the missionaries and to whom he gave a stipend.

[1][36] On the same day, after his lord's death, Yasuke joined the forces of Nobutada, Nobunaga's eldest son and heir, who was garrisoned at the nearby Nijō-goshō imperial villa.

[1][36] There are no historical documents to show the true meaning of Mitsuhide's statement, and it is not known whether it was a sign of his discriminatory mindset or an expedient to save Yasuke's life.

[9][37] It is certain that Yasuke did not die, as Luís Fróis wrote five months after the Honnō-ji Incident, thanking God that he did not lose his life.