Protoconch with one and a half whorl, the apex is dull, high, smooth, lustrous oval, carnicolor when fresh, gradually becoming darker and horn coloured become the same color as the body whorl Columella very narrow, umbilicus transparent when seen from below, columellar margin with weak edge, columellar fold weak. Length 37.3 mm, width 13.6 mm, number of whorls 8 1/3. Another specimen: 33.7 mm x 12.4 mm and with 8 whorls. This genus could be classified close to Metula, the animal has no radula as is concluded by Dr. Tadashige Habe after anatomical examination of a specimen. The operculum is small, thin, oval, light yellow in colour, the nucleus in almost terminal position."

The genus Kanamarua is characterized by a lens-shaped shell with lens-shaped aperture, a glossy surface with fine and sharp spiral incisions, and a narrow columellar lip. The protoconch is rather blunt, with 1 to 2 1/4 glossy, convex, always smooth whorls. The ground colour of the teleoconch is ranging from white, pale yellowish brown to flesh coloured, occasionally with a flamboyant pattern of dark brown spiral bands with alternating white and brown axial strikes.
No radula was found in K. adonis by T. Habe (Kuroda 1951: 71) but recent anatomial investigation on K. narcissisma sp. nov. has show traces of a minuscule radula (pers. comm. Y. Kantor) and some colubrariid features. Metula H. Adams & A. Adams, 1853 is similar in shape but differs by having a granulated spiral sculpture, sharp axial ribs and strong spiral cords on the apical whorls and a multispiral, rather sharp protoconch. Protoconch morphology in Metula is quite variable in number of whorls and in shape, ranging from 2 up to 4 whorls and with or without a spiral fold.
Metula amosi Vanatta, 1913, which is the type species of the genus Metula H. Adams & A. Adams 1853 (Emerson, 1986: 27-30), has a granulated sculpture and a multispiral protoconch.
Iredalula Finlay, 1926 may be similar in sculpture but differs by having broad spiral interspaces, laterally slightly flattened whorls with a more angulate shoulder and a shorter base in combination with a broader siphonal canal.
Bouchet & Waren (1986: 482) suggested that Kanamarua might end up in the synonymy of Anomalosipho Dautzenberg & Fischer, 1912 (type species Neptunea (Sipho) verkruzeni Kobelt, 1876, by original designation). Anomalosipho verkruzeni (Kobelt, 1876) differs in having a rather thick and more porous shell, a broader aperture, an assymetric and slightly curved operculum with terminal nucleus (instead of oval), a thick greenish periostracum and a buccinid radula.