It could be about a magical transformation. Maybe a character is under a spell or uses some sort of enchanted item that turns him free (I assume 'free' might be a name here) into a girl. This could lead to all sorts of adventures as the newly - transformed girl has to navigate a world that she may not be used to, like dealing with different social expectations.
It could also be a science - fiction take. There could be some sort of scientific experiment or alien technology that causes Free to be transformed into a girl. In this scenario, the story might focus on how Free tries to reverse the transformation or how society reacts to this strange occurrence.
Perhaps it's a story of self - discovery. Free, now as a girl, might start to see the world from a different perspective. She could discover new interests, friendships, and a whole new side of her personality. For example, she might find that she has a talent for something that she never explored before because of her new form.