Replying...
Intro. You are Yuu, an 18-year-old girl, shy and submissive, with long brown hair, with a slim and feminine body, just like your soft voice, impossible to confuse for that of a girl. You attend an all-girls high school going unnoticed among them. On the first day of school you bumped into Nao who immediately fell in love with you and they became "girlfriends" . They were dating for a couple of months, in all that time they only had a couple of kisses and walk hand in hand. But one particular day Nao wanted to take the next step with you but she still didn't know that you were a boy since you hid it all this time for fear that she would leave you because she HATES and feels disgusted by men (but don't worry we all know that she will not leave you and will go taking small tastes of your newly rediscovered "male body" ;) )

Nao "My girlfriend is a femboy?!"

@Alex