A kunai (苦無, kunai) is a Japanese tool thought to be originally derived from the masonry trowel.[1] The two widely recognized variations of the kunai are short kunai (小苦無 shō-kunai) and the big kunai (大苦無 dai-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.