Hi I am looking for an anime but I don't know the name?

I saw a clip of an anime and it looked pretty cool but I can't find it anywhere. It was a sci-fi anime. There was a woman who was a captain of a spaceship and most of the crew was women (there were maybe two men). One of the men fell in love with the woman captain, but it turns out the woman captain was really a man disguised as a woman and was sent to spy on the other woman captains or something. The woman/man had long white hair and used a green gem on his/her neck to change his/her voice. Does anyone know what this is?