On the rare occasion that ANYTHING touches a Ninja’s head, it will be damaged. If a kickboxer were to kick a ninja in the head, the kickboxer would suffer brain damage for several reasons that would be blatantly obvious to any REAL ninja. It’s karmic reciprocation.
That doesn’t include the more short-term consequence of the foot crumpling like a twig.
Karma is a harsh mistress 
[QUOTE=BlueTravesty;750001]On the rare occasion that ANYTHING touches a Ninja’s head, it will be damaged. If a kickboxer were to kick a ninja in the head, the kickboxer would suffer brain damage for several reasons that would be blatantly obvious to any REAL ninja. It’s karmic reciprocation.
Karma is a harsh mistress :D[/QUOTE]
You can’t find a ninja’s head through the thick cloud of gas emanating from their front and rear ends.