Pristiophorus japonicus has a long, narrow, and narrowly tapering rostrum (rostrum length is 26-29% of TL), distance from rostral tip to barbels about equal or slightly greater than distance from barbels to mouth (1:1.1-1.2); distance from rostral barbels to nostrils about equal to distance from nostrils to 1st gill slits. About 15-26 large rostral teeth on each side of the rostrum in front of the barbels, 9-17+ behind them; distance from mouth to nostrils 1.1-1.2 times internarial space. Tooth rows 34-58 in upper jaw. Dorsal and pectoral fins covered with denticles in large specimens. Lateral trunk denticles largely unicuspidate. First dorsal fin origin behind free rear tips of pectorals by eye length or more (Ref. 247).

Caudal fin almost straight, with slender upper and lower lobes; pectoral well developed but are not ray-like (Ref. 6871).