Branchiostegus japonicus has an elongated, fusiform body with slightly oblique jaws which reach back as far as the front third of the pupil.

There are also a number of irregular reddish blotches on the back in the middle of the body, these give the impression of the mucus coating having been locally stripped away to show the underlying golden-yellow hue.

[4] Branchiostegus japonicus was first formally described in 1782 as Coryphaena japonica by the Dutch naturalist Martinus Hottuyn (1720-1798) with the type locality given as Nanao in Japan.

[5] When the French naturalist Constantine Samuel Rafinesque (1783-1840) created the genus Branchiostegus in 1815 he used Lacépède's Coryphaenoides hottuynii as the type species.

The larger, more aggressive males are more easily caught and the fishing effort has increased as the catch has declined, an indicator that management of this fishery is required.