This agreement which was negotiated by Leonel de Sousa, captain-chief of Japan's voyage, opened a new era in Sino-Portuguese relations, because since 1522 the Portuguese were officially prevented from trading: several embassies had failed and trade was carried out as contraband and fought by the authorities, who considered them 'folanji' fighting them as pirates.
Leonel de Sousa, the chief captain of Japan's voyage, arrived at the coast of Guangdong in 1552, where he learned that all foreigners were permitted to trade there for the fee payment, except the 'Folanji' (the pejorative name for the Europeans and for the Portuguese in particular, which were considered as pirates).
In 1554 Leonel de Sousa, together with the chief captain of Chaul, made an agreement with officials of Canton to legalize the Portuguese commerce, on conditions that they would pay the stipulated customs duties.
[2] The only written testimony of this agreement is a letter from Leonel de Sousa of 1556 to the Infant D. Luís, where he affirmed that the Portuguese were to pay the fees and not to erect fortifications.
The letter is one of the most important documents in the history of Sino-Portuguese relations, describes the prolonged negotiations with the superintendent of the navy of Canton, the Haitao Wang Po, identified in the Chinese sources as that who had accepted a bribe of the Portuguese by letting them pay taxes in Canton.