The Japanese are record keepers who like unusual things.
The literacy rate has always been high.
Few foreigners settled in Japan before the Meiji era, but if they were active, there are detailed records.
Stop fabricating and spreading false history.
Yasuke are not samurai.
A samurai is someone who has a family name and earns a stipend, similar to a noble in the West.
He is recorded as a baggage handler and does not even carry a sword.