A tanto is a Japanese sword with a blade length of less than a foot, shorter than a katana or wakizashi. It's most famous use was to slice open the stomach during seppuku. Historically, they were often worn along side of a tachi or katana though they were mostly used in a utilitarian fashion rather than a weapon. They were gradually phased out in favor of the wakizashi, which was better for using as a backup or off hand weapon. It was often often carried by women and is easily concealed because of its diminutive length.