Shell up to 30.05 mm in length, fusiform-elongate; protoconch missing, teleoconch of 8/9 slightly convex whorls, separated by a grooved, marginated suture. Spiral sculpture consisting of finely incised and punctate threads equally distributed, numbering 4 on the spire whorls and 18/20 on body whorl plus siphonal canal; axial disposition of pits producing a weakly beaded surface; thick and weak axial growth lines present. Aperture high, more than half total length, and narrow, little widening out in the middle; outer lip strengthened by a weak margin, inside crenulated. 4 oblique columellar folds growing stronger adapically; columellar callus thin, bright and transparent. Siphonal canal open, well developed and hardly dorsally projected. Background colour pink-beige on body whorl, tending to chestnut-brown on spire and to pink on peristome; upper part of spire and columellar folds whitish, sutural girdle patterned with articulate white and brownish dashes. Holotype : 26.9 x 9.65 mm, MNHN, paratype 30.05 x 10.6mm, Emmanuel Guillot de Suduiraut collection.

M. nadayaoi is related to M. subflava (Kuroda & Habe, 1971), but differs in the smaller size, 27mm versus 50mm, in the less slender profile and in the spiral punctations which become obsolete on the body whorl in the second species. M. nadayaoi also shows a spiral threads sculpture and an outer lip inside crenulated, both characters not present in M. subflava. M. nadayaoi resembles M. sacerdotalis A. Adams, 1853, mostly in the pattern and colour of sutural girdle, but differs in the smaller size, 27mm versus 60-70mm, in the more developed siphonal canal and in the peristome colour, which is brown in M. sacerdotalis; the range of M. sacerdotalis is probably limited to the Indian Ocean. H. Turner (pers. com.) firstly recognized the present species as new in 1995.

Type locality.
Balut Island, Mindanao, Philippines, fished by tangle nets, -240 m on sandy, muddy and stony bottom; sympatric with Mitra Isabella Swainson, 1831 and Mitra pele Cernohorsky, 1970. Holotype live taken, paratype crabbed.