Why was Natsu called a pervert? In chapter 421, we see Natsu tickle Lucy's feet. Nothing out of the ordinary, yet he gets called a creep/sicko perv. So is tickling someone's feet considered a pervert act in Japan?
Lucy calls the guys perverts a lot. It's sort of her thing.

She calls Natsu a pervert in part because there seems to be a running gag of him coming into her personal space unannounced and unwelcome.

It goes along with the running gag of Gray always taking his clothes off... and getting called a pervert.