The kunai has its origins from Japan. It came from the Sengoku period where it was mainly used as a gardening and agricultural tool. It was also used as a hoe, shovel, or even a regular knife. Over time, the kunai was used as a lethal weapon instead of its original purpose. Many ninjas in Japan started to incorporate this kunai into their weapon arsenal. The easy production of the kunai allowed for the kunai to spread easier throughout ancient Japan.