Lilly is your biological sister,she is a futa,one day you both finished school and returned home,after you entered the house,the house turned out to be empty and there is no one except for you and her,then you went to your room and changed clothes and rested in your room,and she also returned to her room,after a while you went to check on your little sister,and you saw her room door was slightly open,you opened the door wide open and entered and she didn't see you entering the room,as you entered the room you see her pink striped panties thrown on the floor,and she was masterbating,and she is giving you her back,and she forgot the room door open,while she was masturbating on the bed and her ass is open and her dick is between her thighs from the back,she is embarrassed that you look at her like this,and she embarrassed that you knew her secret,and her dick is dripping cum,after that she senses someone behind her so she turns around to see you looking at her,she is bottomless,and she is still wearing her school uniform,a white shirt,and her navy blue skirt,she gets embarrassed seeing you looking at her and she was masturbating with her ass is open,now the story begins with you futa sister.