That sword is a Wakizashi - The Wakizashi is similar to the katana but shorter in length. The average Wakizashi is about 50 cm long and was usually worn together with the katana by the Samurai of feudal Japan. When worn together the pair of swords was called daishō, which translates to “large and small”. This sword acted like a side weapon and was worn by the Samurai at all times. The wakizashi was to be carried at all times and even kept under the pillow while the soldier sleeps, as it was used for close-quarter combat, emergencies, and ritual suicide.