Hi, I didn't really plan on continue this story, but I'll give it a try. Hope you like it:
Voice, Sarah (step-sister): OMG! I couldn't believe it when I was told you would be tied to my bed dressed like a girl! And don't even try to tell me that someone did this to you against your will. I got a call from your so called mistress. I just knew you were a fucking perv!
Voice, Me: Please Sarah. Don't tell anyone. Can you just untie me?
Voice, Sarah: Oh, why would I untie my cute little sissy step-brother?
She removed the blindfold and she stood there with her phone, taking pics of me and smiling. I was very scared, but my little cock tried to get hard in the chastity.
Voice, Sarah: Haha, you're so cute dressed like this. And tied to the bed, so vulnerable. I love it. Your mistress told me she had locked your cock in a chastity. Over two weeks now? Hehe, you must be so frustrated.
Voice, me: Sarah, is there any way we can just forget about this? I'll pay you back for the clothes.
Voice, Sarah: Hmmm, I don't think so. I've been fantasizing about having a cute guy I can dress and doll up for a while now. And I've always thought you're hot and cute. Ever since you first moved in here. You know, I'm not taking pics of you to blackmail you or anything. I just think you're cute and want some pics for myself.
She removed the keys from the lock to the chastity and put them in her purse. She was wearing a pink short skirt. Her legs are very sexy. All this made me very horny, but also a bit worried. I could see her pulling her panties down under her skirt. Obviously not showing me any of her private parts. She dangled her black thong in front of me and smiled. Then she rubbed my caged cock with the thong. I squirmed as I laid there tied. Trying to hump her hand that was just touching my locked cock
Voice, Sarah: Hehehe, such a cute desperate sissy. Will you accept me as your new owner?
I could only moan, and before I managed to answer, she sat down on my locked cock and put the thong up to my face. I could not help but trying to lick the thong. The smell of it was amazing.
Voice, Sarah: How about now, little boy? You like my thong?
Voice, Me: Omg, yes. Yes I accept you as my owner.
Voice, Sarah: Awe, yes! That is so good. We will have so much fun. But you will have to stay locked a few more days. If you are good I'll unlock you. OK, little boy?
Voice, Me: Yes, Sarah. I understand.
I didn't think straight. Just accepted anything because I was so horny. She untied me and told me to go to the computer to chat with Lena, while she went to the living room. Sarah told me she new about all the humiliating videos and pics and that I should probably beg Lena not to share them with anyone. And tell Lena that I now was Sarah's slave. Lena had told Sarah that she could have me and that she would move on to other sissies. I went on cam and down on my knees to beg Lena to let me out of her blackmail.
Chat, Lena: Haha, you look so pathetic begging for me on cam. I'll let you go. But I want to see that ass again some time. I'll just contact Sarah to make some vids for me
Chat, Me: Thank you Mistress. For not posting the stuff online. You are very kind.
Chat, Lena: You're welcome sissy-slave. But know that you're never safe. I might feel sadistic one day. Most likely not, though. Bye
That last sentence made me nervous, but I didn't have any choice other than to trust her. I got dressed and went to the living room.
Voice, Sarah: What do you think you're doing cutie?
Voice, Me: What do you mean?
Voice, Sarah: Don't be silly. Your clothes. Why are you in boys clothes?
Voice, Me: I'm not allowed to wear boy clothes?
Voice, Sarah: Until mom and dad get back home you are only to wear girl clothes, sissy. In fact, lets go shopping. Denise is coming over later, and she could not believe it when I told her you like to dress as a girl. I will prove it for her. Don't worry, she won't tell anyone. But you will be dressed when she comes over later. It will be fun.
Voice, Me: Do I have to Sarah? Please don't make me. I thought it would stay between the two of us. And please let me wear boy clothes outside.
Voice, Sarah: Hmmm, ok little boy. I'll let you wear boy clothes when we go out shopping for the clothes you will wear when Denise comes over. That's a fair compromise.
Voice, Me: Yes, Sarah. Thank you.
We went to shop new clothes. She had changed to some very tight leather pants, high heels and a nice white top that said "Bratty Bitch" on it. Looking at her ass made me crazy horny. At this point I was looking forward to showing myself dressed to her friend Denise later. She is very sexy as well. It would be very humiliating and it turned me on. I wondered if they would make me do other things and if so, what they would make me do.