It's not so much the motion needs to be faster than you need to be a bit more judicious in placing the keyframes and inbetweens, the swings are fairly weightless because they don't have much follow through or anticipation. If you used only one or two frames for the actual slashing motion and devoted more to the beginning and end it would seem a lot more real. Also, a bit more motion on the ninja's(?) body would be good, he just kind of freezes. That said, I like this anyway, nice work!

Super smooth, just speed it up and it'll be great.

The slashes are supposed to be way faster, but I'm limited to animating in iaza.com for now so I can't post it at its full speed.

Need to speed the slashes and add one more frame when putting away the sword.

Looks awesome! I agree that the sword motion should be faster though. It looks to slow for the rest of the movement.

Sweet animation, maybe make it a little bit faster? Just the sword motion though...