This species is restricted to the western North Pacific in the seas around the Japanese Archipelago.

[1] It has also been reported from the Kuril Islands east to the central and eastern Bering Sea.

[4] Gonatopsis japonicus appears to mature at a relatively small size of approximately 150 mm in mantle length,[1] and this is indicated by the development of hooks on the arms and the drak pigmentation of the beak.

The regular capturing of juveniles and young adults in the surface layers suggests that this species is an active vertical migrant, it further suggests that its ontogenetic descent takes place relatively late in its life cycle.

In the Okhotsk Sea measurements of mature and pre-spawning males from the mesopelagic and bathypelagic zones gave mantle lengths which ranged from 278mm to 478mm, while immature and maturing females mantle lengths ranged from 398mm to 582mm.