Actually Sakura is a trap (a boy dressed as a cute girl) and a transvestite, which is someone who just likes to dress as the opposite sex and has nothing to do with sexuality. Note that, he doesn't want a sex change, he wants to act as a good boyfriend, and he's attracted to Amane because she's a girl. Amane, on the other hand, is transgender. She dresses as a boy because she identifies as one. In addition to that, she's attracted women and possibly may have feelings for Sakura because she resembles and has the mannerisms of a female.