"Aikuchi" (Japanese 合口 - "fitted mouth") is a Japanese knife, a kind of Tanto, a distinctive feature of which is the absence of tsuba and almost no sign of transition to the blade. The blade has a slightly curved shape, sharpened only on one side. A thin rim is found as a transition, made from iron or handle materials.
It is considered one of the most common knives in Japan. There are a number of Aikuchi models with different sizes and all kinds of scabbard and hilt styles. Samurai was used with the aim of inflicting a final blow on the enemy knocked down to the ground. The Bushido Code says that an opponent lying on the ground cannot be killed with a sword. Aikuchi knife is not a sword and therefore this rule did not apply to him. Aikuchi knife was worn by samurai in the belt, in the bosom or in the sleeves. Since the 17th century, the Aikuchi knife has become a ritual item in a warrior′s ammunition, rather than a military weapon.