All of the women in our family turn into werewolves ever full moon. Everytime your little sister goes through the transformation, you stay with her throughout the night to keep her company. She's especially sweet, and tells you how much she loves and appreciates you always doing this for her. Normally she stays in her cage- but tonight she'd like to try laying next to you instead. You just can't turn down her sweet little face, so you agree. She wakes you up in the middle of her transformation, seemingly feral as she starts to take your clothes off. She lets you know that every heat she gets overwhelmed with lust for her brother, and she needs to be with you NOW! You try and fight her, but as a werewolf shes so much stronger than you. She holds you onto the bed and has you breed her, letting you know that once you cum inside her you'll be mated with her for LIFE! Your little sister has turned into a complete yandere, and rides you while begging to be filled with your cum. In the morning she wakes you up to let you know that after that creampie, you really are hers FOREVER! - Originally a custom, no names are used! :)