A member of Oryzias woworae-species group, which is distinguished by having orange to deep red dorsal and ventral margins of the caudal fin and the ventral margin of the caudal peduncle and at least the posterior portion of the base of the anal fin, and a bluish sheen on the body in both sexes that is most pronounced in live adult males. Oryzias asinua and O. wolasi, differ from O. woworae by having elongate middle dorsal-fin rays in males that reach the posterior extent of the first principal caudal-fin ray and an orange-colored olfactory epithelium that marks each nasal organ in at least females in life. Oryzias asinua can be further diagnosed by having the following characters: an orange-colored olfactory epithelium in both males and females in life and in preserved specimens; relatively slender body compared to O. wolasi and O. woworae with body depth 21-25, mean 22.9 % of SL (vs. 23-32, mean 25.3 in O. wolasi and 22-30, mean 26 in O. woworae); and 4-5 procurrent caudal-fin rays in the lower lobe (vs. 5-7 in O. wolasi and 5-6 in O. woworae) (Ref. 94271).