Ninjaken

The Ninjaken, also known as the Ninjato of Shinobigatana, are blades characterized by being straight, chiseled edged swords. They appear to be largely a media creation, based on the design of the Wakuzashi.

What sets a Ninjaken apart from more commonly recognized blades such as Katanas are the straight edge and square guard. This was said to be a more efficient and sensible weapon for the ninja, who relied heavily on stealth tactics.

Leonardo is commonly shown using Katanas throughout most continuities. In the 2007 Movie, however, his blades were clearly rendered as being straight with square guards. Confusion between the two different swords may be due to simple confusion, since the Ninjaken and Katanas have minute differences.