Hourou Musuko (Wandering Son)

The story depicts a young boy named Shuuichi Nitori who wants to be a girl, and his friend Yoshino Takatsuki, a girl who wants to be a boy. The series deals with issues such as transsexuality, gender identity, and the beginning of puberty.

I'm still watching this, having a hard time to finish it actually. Well, this one caught my eyes :)