One thing i want to point out:
Katana, wakizashi and ninja-to are three totally different weapons.
(Ive made some research from Wiki to be sure that i dont say anything wrong)
The word katana was originally used for "one edged sword". Today, the term is used to describe the sword "nihonto". It is a curved blade used by samurai, its length is 70-90 cm.
Ninjato is a straight blade used by ninjas, its shorter than the katana.
The wakizashi is a shorter version of the katana. Its about 50 cm. Its also used by samurai.