In 1542, Matsuura Takanobu protected Ōshio and established the foundation of a trading port; in 1550, Portuguese ships arrived and southern barbarian trade began. The Matsuura incorporated wokou (Japanese pirates) and foreign merchants, leading international trade in northwestern Kyushu.
Since some scholars dispute Hirado as the site of Portuguese ships' first arrival in Japan, 1542 is used—when Ōshio's protection established the port market.
Certainty: MediumHow far the account above is supported by the cited sources. It does not refer to the precision of the coordinates or the dating.