The term shuriken did not just refer to the well-known ninja's throwing stars. Shuriken was also used to denote any instrument or tool thrown by a ninja, such as knives or darts. ¹⁾

The most proficient ninja clans in Japan were from the Iga and Koga (Koka) areas. Because of their geographical location, these ninja clans thrived in their abilities. They were protected because they were isolated between two mountain ranges. ²⁾