A kunai is a Japanese tool thought to be originally derived from the masonry trowel. The two widely recognized variations of the kunai are short kunai and the big kunai. Although a basic tool, in the hands of a martial arts expert, the kunai could be used as a multi-functional weapon. The kunai is commonly associated with the ninja, who used it to gouge holes in walls. Many popular manga characters use kunai as both their primary and secondary weapons.