A kaiken (懐剣) is a 20–25 cm (8–10 in) long, single or double-edged dagger without ornamental fittings housed in a plain mount.
It was once carried by men and women of the samurai class in Japan. It was useful for self-defense in indoor spaces where the long blade katana and intermediate sword wakizashi were inconvenient. Women carried them in their kimono either in a pocket-like space (futokoro) or in the sleeve pouch (tamoto) for self-defense and for ritual suicide by slashing the veins in the left side of the neck. When a samurai woman married, she was expected to carry a kaiken with her when she moved in with her husband.
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- Minoru, Nishio (1985) . Nishio Minoru; Iwabuchi Etsutarō; Mizutani Shizuo, eds. Iwanami kokugo jiten (in Japanese) (3rd ed.). Tokyo: Iwanami Shoten. p. 155. ISBN 4-00-080003-5.
- Nihonto message board forum
- Richard Stein's Japanese sword guide
- Japan Arts Council e-book Mamori-gatana pp. 179–180