Oxygyne hyodoi is described in Abe & Akasawa (1989) from the island of Shikoku/Japan, an island southeast of Japan mainland. The authors address the remarkable disjunction of this genus between the West African Oxygyne triandra (discovered by Rudolph Schlechter September 1905 in Moliwe/Cameroon, published in Schlechter 1906, and not found since then) and this new species. In the same publication the authors transfer Saionia shinzatoi, found on the Ryukyu Islands (southwest from Japan) and coined by Hatusima (1976), to Oxygyne shinzatoi. However, since the description of Hatusima (1976) was not in accordance with the rules of the International Code of Botanical Nomenclature (today ICN = International Code of Nomenclatur for algae, fungi and plants) because two specimen were cited as holotypes, the transfer done by Abe & Akasawa (1989) was also invalid (see passage on Oxygyne shinzatoi). Nevertheless, the description of O. hyodoi is effective, and discerns the new species from O. triandra and Oxygyne/Saionia shinzatoi by the shape of the perianth lobes, the style with three clavate appandages, and the shape of the annulus lobes more or less constricting the perianth tube opening.
Interestingly, Suetsugu et al. (2020) rediscovered O. hyodoi at the type locality!