Why the Nara Wear Ponytails

I finally have some time to draw again, so this little comic was to get back into sketching and for a bit of fun.

I've seen a lot of images around of Shikamaru with his hair down, and it's always thin and straight, so I'm guessing he's been showed with straight hair at some point. But honestly? That makes no sense at all. He actually has pretty long hair, and when in a ponytail it's standing straight up! His hair must be thicker and more spiky than Naruto's! Anyway, it would make so much sense if this was the reason for the ponytail. I can't imagine the Nara bothering with their hairdo much, so unless they just shaved it all off then this would be an easy way to get it out of the way  

Shikamaru Nara (c) Masashi Kishimoto.