The kaiken (懐剣) is a small Japanese sword, smaller than the tantō, which is more like a knife in size (about 15 cm).
It was carried by samurai women, either in the sleeves of their kimono, or passed through their obi.
In addition to its role of defense of the one who held it, the kaiken carried in him two symbolic values of which one particularly decisive:
- the kaiken was generally offered by the husband, or the family of the husband on the occasion of the marriage and marked the indefectible bond of the wife to her husband; to lose it or to separate from it was significant of dishonor with the consequences which we know in the feudal Japanese civilization;
- in addition, the kaiken was used as a weapon for the jigai, the suicide of the wife by perforation of the carotid artery when her husband, struck with infamy or dishonor, had to give himself the seppuku. The kaiken thus reminded the wife of her dependence on her husband. The kaiken had therefore a similar role for the woman as the wakizashi for the samurai.
Kaiken-jutsu is the Japanese martial art of knife handling.
The kakushi designates the art of handling hidden weapons, such as kaiken and shuriken.