To get Rebecca route, u need to avoid every dark path. The first one is when u drank the potion in the village u will get visions like spiderman and batman after all that visions, the MC will encounter the Devil and he will offer to join him. Make sure to refuse him. And the second one is when ur in the Mansion and ur just about to take the book, the game will give u two choice, either go to the girls scream or take the book. Dont take the book and go for the girls. U will get the book after u leave the mansion. If u done this two u can get Rebecca route. At her wedding make sure to talk yo the pianist and change the wedding song to the Evagelian or something. And ask the Father to stall the groom. If u avoid the two dark path i mentioned, the Father will help u. If u didnt avoid the fark path he will refuse. But all of these will only work if u build up enough points. Hope that helps.