Wakizashi

Wakizashi (脇差) A sword similar to katana but it is shorter (blade between 12 and 24 inches). Often worn together with katana. When worn together they were called daisho. According to traditional samurai law (Bushido), it is used only to commit hara-kiri. After the 16th century it was sometimes used in the off hand to the katana, a technique pioneered by Miyamoto Musashi.
See also katana, tachi, tsurugi.

Katana (top) and wakizashi (bottom)