For those who can't read Chinese ('Kanji'), some of the portraits cover Vietnam, Yunnan, China, India, Korea, Thailand, Mongolia and the Philippines as well as Japan. Possibly also some other areas in northeast Asia, I am unclear on the period terminology. As they are dated 1820s but seem to use Chinese terms from earlier periods, I guess this was an adaptation of an earlier set of Chinese descriptive texts or (heresy to suggest!) images that had been carried to Japan. But that's just supposition.