One of the key ports of the Nanban trade (16th-17th century Japanese-Europe:
change of goods, firearms, culture) was Macau. The Europeans arrived the enclave
for a stopover before the Canton fair, where they'd go to buy and sell goods. There
are a lot of depictions of the Portuguese arrival to Japan by Japanese artists,
specifically those painted on biombos (Japanese folding screens) but there are no
depictions of the Portuguese taking off from Europe. Since the artist is himself a
Nanban (foreign barbarian), he decided to paint from the point of view of a 16th century fictional character who sailed from Lisbon. Notice how football team flags are used instead of national flags.