Setting Your Game In The Ryūkyū Kingdom

The Ryūkyū Islands, which are today part of Japan, were a wealthy trading kingdom (the Ryūkyū Kingdom 琉球國) in the 16th century. The kingdom was nominally a tributary state of Míng Dynasty; however, following the Míng policy of ending sea voyages gradually put in place during the 15th century, and also due to the increased threat on maritime travel posed by the Wōkòu (倭寇), the Kingdom was de facto independent.

The archipelago has been united in the first half of the 15th century by Shàng Bāzhì (尚巴志), who is also the founder of the ruling Shàng Dynasty. The capital city is at Shuri (首里) on the largest island: Okinawa (沖縄).

The reign of Shàng Zhēn (尚眞, 1477–1526) is widely regarded as the golden age of the island kingdom.

Despite the presence of a ruling aristocratic class, the Ryūkyū Islands have an egalitarian society. In particular, no native Ryukyuan may ever be bound into slavery — all slaves on the islands have been bought from foreign traders, and are usually Chinese or Korean victims of coastal raids by the Wōkòu.

The upper nobility (who are the descendants of Chinese gentry families from Fújiàn who arrived in the 14th century) have Chinese-style names and are bilingual, Chinese and Ryukyuan; the rest of the population have local names and are monolingual. Ryukyuan is a language related to (but different from) Japanese.

The Ryukyuan religion is a mix of ancestor worship, nature worship (the Moon and the Sun), and shamanism. Due to Chinese and Japanese influence, Buddhism is making inroads; there are Japanese Buddhist missionaries from Kyōto on Okinawa, and they have built four temples.
Irrespective of the particular strand of religion, all celebrants are female; some of them are “druid”-like, some others more like Inner Asian shamans.
Spirits and magical creatures such as yāoguài (妖怪, see p112 of The Celestial Empire), dragons, guardian lions, and ghosts, are very present and of paramount importance in the local folklore.
There is also a big emphasis placed on the fabrication and the use of amulets, talismans, etc. Lóngmài (ley lines, see p85 of TCE) strongly influence Ryukyuan magical and religious practices.

The islands are covered with all manner of moist forest and other tropical and subtropical flora. There aren't any large predators; the only danger when travelling overland are venomous snakes.

Map of Okinawa