(Glassell, 1933)
Male: Small, but considerably larger than the other congeners of the genus Sakaina.
Carapace well calcified, transversely oblong, with its lateral borders weakly convergent backwards; anterior border weakly convex as a whole, and posterior border almost straight; dorsal surface evenly convex in both directions, smooth without indication of areolae, provided with a rim of pubescences behind frontal lobes and on each antero-lateral border; a pair of small patches of pubescences on cardiac region.
Abdomen abruptly narrowed from fourth to sixth segment, with terminal (seventh) segment widening distally and weakly concave at median part of distal margin.
All thoracic appendages stout, with dense pubescences. Both chelipeds equal in size and shape, being provide with denticles on cutting edges of both fingers. In first three pairs of ambulatory legs, carpi and propodi swollen; dactyli bent inwards, acutely pointed at each tip which is semi-translucent and amber-coloured.
First pleopod sickle-shaped, tapering to a pointed tip, with simple setae at main part and with plumose setae at basal part.
Female: The female is somewhat smaller than, but generally quite similar in shape to, the male. The dorsal surface of the carapace is smooth, and has also a rim of pubescences, but occasionally patches of pubescences are absent from the cardiac region. The female carapace is proportionally broader than that of male; mean CW/CL ratio of 13 females and 11 males are 1.60 and 1.45, respectively.
The abdominal segments are rather narrow, weakly diminishing its width distally, with slightly convex lateral margins of fourth to sixth segments; terminal segment is subtrapezoidal in outline. (Takeda et al., 1991)
Type locality: Mutsu Bay, Japan.
Range: Japan - Mutsu Bay (Yokoya, 1928), Hakodate Bay, off Tomakomai, off Ohmu, off Sawaki, off Okoppe, off Saruru, off Yuhbetsu, and off Tokoro (Takeda et al., 1991), off Ohmu, Okkobe, Wakkanai, and off Tomakomai (Komai et al., 1992), Soya Strait (Takeda & Miyauchi, 1992).