I've watched enough japanese softcore porn to know ~chau is a girly structure. i didn't know nakucha was strictly a girl thing, but i still wouldn't have used it, largely due to this...
http://www.youtube.com/watch?v=dzjK92fZfzM
As much as thats possibly the best the video ever made, I don't think talking like that would help me pick up any chicks... god ninjas are awesome.