Type locality of Rhynchobatus mononoke, Kagoshima, off Satsu-masendai. Known off the western coast of Kyushu south to Kasasa, Satsuma Peninsula, north to Nagasaki, west to the northern East China Sea, and of Tateyama, Boso Peninsula. Most probably endemic in the country (Ref. 123186).

Conservation status: This wedgefish is occasionally landed at fish markets in Kagoshima Prefecture and used for culinary purpose. Reported catches of the species were very rare in the East China Sea and is apparently restricted distribution and increasing rarity indicate that the species should immediately be included in the IUCN Red List CR 'Critically Endangered' category (Ref. 123186).