Kaidā glyphs

Examples of Kaidā logograms
(from Sasamori, 1893)

Kaidā script (Yonaguni (Dunan) Ryukyuan endonym: Kaidā dī / カイダーディー; transcribed to Japanese: Kaidā ji / カイダー字) is a writing system of unknown provenance once used in the Yaeyama Islands and on Yonaguni, the southwestern-most of the Ryukyu Islands in Japan. They were primarily used along with Suzhou numerals for economic records: taxes, business transactions, crop and fishery yields, and the like. During the Meiji period they were used for postings in primary schools; they were evidently accurate enough to make corrections to official announcements. Although some Kaidā tax records on wood are preserved in the National Museum of Ethnology, the overwhelming majority have been lost or discarded over the years, particularly those written on material such as leaves. They are currently used on Yonaguni and Taketomi for folk art, T-shirts, and other products, more for their artistic value than as a writing or record-keeping system. Distinctions that were optional in Yonaguni were reflected in Kaidā writing, as there are separate glyphs for commercially important distinctions like mare (mīnma) and stallion (biginma).

Discovery of kaida writing by outside visitors

The first non-Yaeyaman author to comment on kaida writing was Gisuke Sasamori (笹森 儀助), who left copies of many short kaida texts in his Nantō Tanken (南島探検, Exploration of the Southern Islands), a record of his 1893 visit to Okinawa which also mentions the hard labor imposed on the islanders by the regime. Around the same time, British Japanologist Basil Chamberlain visited Shuri on the main Okinawa Island and, while unable to reach the Yaeyama Islands, copied single kaida characters and reproduced them in Luchu Islands and Their Inhabitants, published by the Anthropological Journal of Great Britain and Northern Ireland.

In 1915 the mathematics teacher Kiichi Yamuro (矢袋喜一) included many more examples of kaida writing, barazan knotted counting ropes, and local number words (along with a reproduction of Sasamori's records) in his book on Old Ryukyuan Mathematics (琉球古来の数学). At this time kaida writing was still in daily use, but by the time anthropologist Tadao Kawamura (河村 只雄) made his anthropological study of the islands in 1940, the imposition of the Japanese language had accelerated and kaida writing was in decline.

With the abolition of the "head tax" in 1903, the primary impetus for kaida writing had been removed, but it lived on in the form of personal record keeping and even in sending packages (Kawamura 1941). In the 1930s the imposition of the Japanese language became more stringent, with the infamous dialect cards hung around the necks of children who insisted on using the local language, and kaida writing began to disappear. Today only a few elderly residents of the Yaeyama islands can remember the active use of kaida writing, and local record-keeping has long since been changed to Japanese.