While the katana is the most famous, it’s far from the only type of Japanese sword. Some feature massive blades that require two hands to wield, while others are compact — more like a dagger or knife. Among the smaller styles is the kaiken, a hidden blade steeped in symbolism. No, it’s not the name of some mythical sea monster. It’s a real Japanese weapon. But do you know what the kaiken really is? Who carried it? What was it used for? And does it still have a purpose today? Let’s dive into the story behind this unique mini katana.
Description of the Kaiken
The kaiken (懐剣) is classified as a Japanese sword, even though its small size might make it look more like a knife to Western eyes. Typically, the kaiken measured about 5.9 in (15 cm), though some reached 7.8–9.8 in (20–25 cm). The blade wasn’t standardized. It’s smaller than a tantō, usually straight, and often single-edged. Compact and symbolic, the kaiken was meant for both self-defence and ceremonial use.
Who Carried the Kaiken?
The kaiken was worn by women, especially the wives of samurai. Like the katana and wakizashi, it was sometimes tucked into the obi (belt), but more often, it was hidden from view. Similar to the shuriken, the kaiken was considered a concealed weapon. It was commonly placed in a pocket or tucked into the wide sleeves of a kimono for quick access when needed.
What Was the Kaiken Used For?
Originally, the kaiken served as a self-defence weapon. It was commonly given as a wedding gift from a husband or his family, symbolizing the deep bond — and sometimes dependence — between wife and husband. Losing or discarding it could be seen as dishonourable. If a samurai lost his honour, he would perform seppuku to restore it. In some cases, his wife would be expected to follow him in death.
This ritual was different for women. While the samurai cut across his abdomen with a wakizashi, the wife would pierce her carotid artery using the kaiken — a more discreet but equally symbolic act of sacrifice.
Unlike other Japanese swords, the kaiken is not used in modern martial arts practice. However, it has inspired a knife-fighting martial art known as kaiken-jutsu. Though no longer used today, the kaiken remains a powerful historical symbol from the samurai era — a reminder of its customs, rituals, and the moral code that guided warriors, as passed down through the Bushido.
