The Japanese rubyfish was first formally described as Emmelichthys schlegelii by the Scottish naval surgeon, naturalist and Arctic explorer Sir John Richardson with its type locality given as Nagasaki.

Richardson based his description on an illustration of a fish in part7-9 of their volume on Pisces of the Fauna Japonica by Coenraad Jacob Temminck and Hermann Schlegel which they called called Erythrichthys but did not give a specific name to,[3] Richardson named it in Schlegel's honour.

[4] In 1859 Albert Günther also gave the name Erythrichthys schlegelii to the illustration by Temminck and Schlegel with its type locality as the Sea of Japan, without citing Richardson, 1846, in his Catalogue of the fishes in the British Museum.

[7] They are bluish grey on the upper body, silvery white with pinkish hue ventrallu with reddish orange caudal and pectoral fins.

[2] The Japanese rubyfish has been reported to feed mainly on shrimps in the family Sergestidae, as well as on small mesopelagic lanternfishes, snaggletooths and barracudinas.