It is likely that Yasuke could speak or was taught Japanese, perhaps due to Valignano's efforts to ensure his missionaries adapted well to the local culture. Nobunaga enjoyed talking with him (there is no indication that Nobunaga spoke Portuguese, and it is unlikely that Yasuke would have been able to communicate in classical Chinese, the Asian lingua franca of the time). He was perhaps the only non-Japanese retainer that Nobunaga had in his service, which could explain Nobunaga's interest in him. Yasuke was mentioned in the prototype of "Shinchō ki" owned by Sonkeikaku Bunko (尊経閣文庫), the archives of the Maeda clan. According to this, the black man named Yasuke (弥助) was given his own residence and a short, ceremonial katana by Nobunaga. Nobunaga also assigned him the duty of weapon bearer.