The Ninja Epidemic

You step to the left and avoid watch with satisfaction while the blade embeds itself into the ground. You clobber the ninja in the back of the head with a vicous swing of your bat that sends him sprawling to the ground. You finish him off quickly with two more crushign blows to his head, cracking his skull in half like a split coconut shell.

Another ninja rushes in at you screaming the whole way and you easily dodge his clumsy attack and crack him repeatedly with the bat. Having taken both these ninjas out of the way ,you look around and find the woods quiet and suprisingly free of ninjas.

How can this be?