The main character has to hide himself from the Order (some kind of Templars) In order to do that he must dress himself as a woman (risking his life if they find out) or transform himself into a woman for a limited time (mainly from the daylight). This is still not yet implemented in the game since it will have more weight after the first day, but I would say it's a major part of the game, since transforming yourself into a woman can have its risks if you take submissive actions, where you will become more and more femenine and at the end of the game depending on your choices it may be imposible to be back a man.
But as I said, it's still not implemented.