Wakizashi
The Wakizashi, is a shorter version of the katana, designed for combat in close quarters such as the halls of a mansion. Its reduced length but higher level of sharpness makes it a lethal weapon against unarmored opponents.
The wakizashi sword is one of the most popular weapons used by Ashigaru (foot soldiers) and ninjas. It can be easily concealed and used when the time comes.
Some warriors will combine the wakizashi with a longer sword such as a katana in a dual-wielding stance. The famous Samurai Miyamoto Musashi was an expert in this.