The earliest spears found in Japan were named hoko yari, and were clearly modelled on Chinese spears. They have a hollow slot in contrast to the most common Japanese yari spears which usually feature a long tang (nakago). The tang is affixed to the tempered shaft with pegs driven through holes in the tang in the same way Japanese swords are attached to the tsuka or haft. The term yari became more widespread around the year 1334, but the widespread use of spears increased only after it became common to recruit commoners during the Ōnin War (1467-1477). This occured during the Moromachi Period when full-scale war became commonplace in Japan. Earlier, there were bushi warriors who specialised in spears, but the naginata was by far the more popular polearm. Japanese spears are almost without exception close-combat weapons not generally used for throwing. Various lengths of yari exist and the shape of the blade varies dramatically. During the mid 16th century, long nagae yari spears became common, ranging from 4.5 to 6 metres in length and being designed for fighting in formation. The blade of the yari was made of tamahanage, the same steel used for swords in Japan. Different blade styles include the straight su yari (choku-sō), kama yari, which had sideways-pointing blades in addition to a straight blade. The blades with a triangular cross-section were called sankaku yari, while those with a diamond-shaped cross-section were ryō-shinogi yari. The shaft (nagaye or ebu) of the yari varied between 1 and 6 metres in length. It was made from hardwood covered in laquered bamboo strips. There were also a wide array of cross-sections, ranging from round to oval to polygonal. Usually the shaft was reinforced with metal rings or wires (dogane). The spears also featured a pommel (ishizuki) as a counterweight, and these could be either ball- or spike-shaped.

The spear techniques used in Bujinkan chiefly originate from Kukishinden Ryu. Kumogakure Rye also makes used of the kama yari. Though yari is in the main a stabbing weapon, entire yari is used in techniques in Bujinkan.