The Portuguese nau do trato was known to the Japanese as the kurofune (black ship) or nanban bune, ship of the Nanban, or Southern Barbarians, so called because these foreigners arrive from the south. (The term originated in China, where all foreigners were regarded as barbarians.)
Jesuit missionaries accompanied the Portuguese traders and spread Christianity in Japan, especially in Kyushu, where there were many converts among the local daimyo. Francis Xavier, one of the founding fathers of the Jesuit Order, was the first to arrive, in 1549. Until 1624, there was also a small trade between the Japanese and the Spanish, who were based in the Philippine Islands. Spanish ships sailed every summer from Manila to Mexico on the Black Current and a few entered Japanese ports. A handful of Spanish Franciscan friars propagated their faith in Nagasaki, Kyoto, and elsewhere.

The design depicted on the sides attests to the uncommon creativity with which the Japanese people approached and adapted things Western. The Spanish/Portuguese 48-card deck arrived in Japan in the mid-16th century, supposedly brought by Francis Xavier. It had 4 suits - cups, swords, coins, and clubs - said to represent the four classes of medieval Europe: priests, knights, merchants, and peasants. Some of these four suits are pictured here, plus one that is unique to Japan. It will be noticed that the Japanese, not quite understanding the motif of the chalice, favoured picturing it upside down like a Buddhist jewel, with the stem sprouting from the top. At some point in their passion for European playing cards, the Japanese added a fifth suit, marked by the ‘three jewels’, or tomoe, crest, symbolising bounty. The dragon motif, a feature of the original Iberian set long associated with Portugal, must have been particularly popular in Japan, even though the winged dragon suggests St. George - a Christian motif that surely would have displeased Japanese authorities.

It is possible that this eclectic amalgam of card-characters can be explained by the Japanese association of the Iberians with material bounty because of the rare and precious commodities they brought. The idea of a riches-bringing ship became conflated with the native notion of the takarabune [treasure ship], whose passengers are the Seven Lucky Gods - a common image in folklore. The message seems to be ‘good things come by sea’. The foreign notion of card games caught on like wildfire and was subject to constant regulation by the Tokugawa shogunate, which frowned on gambling. Decks went through various permutations to get around the proscriptions, including the revised pack called Unsum Karuta - a mix of European, Chinese, and Japanese motifs - which is what is pictured here.

For more about Unsum Karuta, see:
Sezon Museum of Art and Shizuoka Prefectural Museum of Art, eds., ‘Porutogaru to Nanban bunka’ ten: mezase toho no kuniguni [‘Portugal and Namban culture’ exhibition : Via Orientals] (Japan, 1993), p. 216-217, 219, no. 206;
and go to the Kyushu National Museum website (Japanese):
http://www.kyuhaku.jp/museum/museum_info04-07.html
http://www.kyuhaku.jp/collection/collection_gl02.html