Your older sister Courtney and you had a pretty decent relationship. Seeing your door open she wondered if you were inside and found a nice doll. She was under the impression you had gotten her something, and just grabbed it and brought it to her room. She was impressed by the maid's uniform as her hands caressed the small things form. You in the bathroom kind of enjoyed the light feeling, but were worried about what you'd do. As her hands felt the maid's chest and felt them she squished them a bit more which you definitely were enjoying the feeling but worried if she fiddled with them too much. Your sister however was feeling some relatively realistic boobs on a doll. Curious about what the doll was made she started disrobing the maid carefully. As she pulled off the uniform it revealed her black underwear and the clothes you were wearing vanished leaving you in your underwear as well... Then the underwear came off. Your sister was a little shocked at how anatomically correct the doll was. Out of curiosity she spread the doll's pussy lips apart to see the small details inside, and her vagina ended up widening a little and you felt your vagina growing as well. Then you sister put the tip of her finger into the hole surprised by how deep it was, but for you it was like someone was cramming a pointy fist into your vagina as you were mostly feeling her well manicured nail.
Then she saw the back which she opened up and your hair fell out of it and she wondered why the word "essence" was inside. However you figuring that this could only get worse would go find whoever was changing you with the doll. Walking out into the hall naked you heard your sister mumbling to herself and looking into her room you saw the gender fluid voodoo doll. You heard her ask "What does it mean by Essence."
Covering yourself you said "I think I may be able to explain sis..."
Courtney looked and asked "Who are you and what are you doing in here naked!?!"
You said "It's me your... once brother. That's a voodoo doll that I was testing and... well you disrobed it so my clothes vanished."
Courtney wondered "Voodoo doll? so..." she tried messing with the doll's breasts but with no essence inside right now no one was affected.
You were curious what was going on and then said "I guess when you opened the back my hair must've came out."
Courtney asked "And how do I know your my brother an-"
"You wet the bed till you were 8."
"Fine, your my brother. So then if this could change you into a girl I wonder..."