Wakizashi

The katana was the "primary" weapon of the samurai. However, often the samurai would carry a second blade, a tanto or wakizashi, to be used as a "backup" of sorts. Also, traditionally it was considered very rude to enter a house without removing your katana at the door. And instead of staying unarmed they would normally leave either the tanto or wakizashi in their belt. Wakizashi are any blade over about 12" long and under about 24" long although most were usually around 18".