Shuriken, or "hand-concealed blades," are small iron-forged projectile blades of two fundamental shapes: flat plate with pointed tips, and straight bar with a single pointed tip. Their purpose was to create a distraction by causing light to medium level injuries, thus provide an oportunity to attack with a larger more destructive weapon that can decisively incapacitate an opponent.

Hand-held projectile weapons were used in the ancient world by warriors in the Middle East, Europe, Africa and Asia. The Judeo-Christian bible tells about young David shooting a stone at the giant Philistine warrior Goliath with a slingshot, the Indian Mahabaratha tells about a flat ring-like projectile used by the god Vishnu, and the Japanese picture scroll of annual events depicts the usage of a slingshot in a brawl.

It would be reasonable to assume that knowledge of metal projectiles travelled from India to China then arrived in Japan from the Korean pennisula, in a process that took a millenia. Then, once in Japan, the Japanese further developed and refined the these projectiles, and even added new types and shapes, to make them what we all know today as shuriken. The shapes and sizes have been developed by different warrior groups in various regions of Japan, to include mainly the multi-pointed metal plate such as the happo-, roppo-, juji and senban, and the single-point bar with a round or square profile, known as bo- or harigata shuriken,among other shapes.

While the throwing stances and motions are quite similar to all types of shuriken, with diffent grips and arm swing being the main differences, each of the two fundamental categories have distinct characteristics. The flat plate shaped shuriken has a considerable better range/accuracy ratio, while the single-point bar has a better penetration power. Also, the former requires less training and skills, while the latter is much more difficult to master and execute efficiently. As a result, organized shuriken units such as those of Takeda mentioned in the Koyogunkan used roppo shuriken, for example, and highly-trained individual special warriors used bo-shuriken.

Modern shuriken training aims to achieve three goals, beyond the mear preservation of tradition. First, to increase control of body movements, and create awareness and sensitivity to the effect of suttle changes in these movements. Second, regular training increases dramatically one's concentration, leading to precision execution of shuriken throwing as well as other weapons techniques. Third, proficiency with shuriken may allow similar proficiency in throwing other similar object in cases of actual need for self-defence.

The demonstration video presents the usage of bo-shuriken as taught and practiced in Genbukan. The video illustrates for the first time some of the unique and hidden throwing styles used by special warriors and samurai.