Your parents had been fighting a lot, which worried you and your sister Sarah, who feared they would end up getting divorced.
One day, out of nowhere, her sister appeared saying that she had won a trip with a companion around the world for a year with all expenses paid. She offered the trip to her parents, saying that getting rid of all the stress of everyday life would be good for them. As she didn't used to lie, no one suspected anything, and after convincing them that you would find a way to take care of things in their absence, they accepted and went on the trip.
You and Sarah have agreed to take turns doing chores around the house. In the first few weeks everything went normally, but then things changed a few things. Her sister started to take longer to wake up on days when she had no obligations in the morning, and she also started spending more time in the bathroom, especially when taking a shower. You didn't make a big deal out of it, as you thought it was natural since you didn't need to take care of your parents' clothes and stuff either. Another thing you noticed was that some of your objects sometimes disappeared one day only to reappear the next day. And sometimes when Sarah prepared the food you noticed that the taste was different, but you just believed that she was just using a new seasoning and that it must be very expensive, that's why she didn't always use it.
It had been four months since you were living alone with your sister when something you never thought possible happened. You went out to meet your friends and on the way you realized you had forgotten your wallet, so you went back to your house to get it. When you walked in you saw that Sarah was in the living room watching TV and when you saw what she was watching you saw that it was a porn movie. You got close to her, who didn't notice your presence, and was surprised to see that she had her skirt up and was stroking a cock bigger than yours that she had between her legs, with equally big balls where you were sure that her vagina was before, as you had already seen it when you were younger.
"Sarah, what are you doing?" You asked and your sister, who took the biggest fright and tried to hide her dick under her skirt, what her erection hindered her from doing and you could still see her balls.
"[your name], what are you doing here? I thought you were out with your friends and weren't coming back anytime soon." Sarah asked
"I just went back to get my wallet that I forgot." you said
"And with that you caught me doing something shameful. And you saw that, didn't you?" Sarah said
"Yes, I saw your dick. But how can you have one? I'm sure you haven't had it before." you said
"Please don't tell our parents about this. I was also tired of seeing our parents fighting and when I learned that a nearby laboratory would pay very well for anyone who agreed to participate in an experiment they were doing to which they needed female candidates. That's when I had an idea and I volunteered, so I could pay for our parents' trip." Sarah said
"You mean you didn't win the trip in a raffle?" you asked
"It's true, I'm paying with the money I'm getting. I had signed up not knowing what the experiment was about, it wasn't until I signed up that I learned that the experiment was one to give a fully functional cock to women. When I found out what it was I was in doubt if it would continue, but if it could be used to save our parents' marriage, swapping my vagina for a dick was worth it." Sarah said
"I won't tell them anything. I would do the same if I had the chance. But even so I think it's just a matter of time for our parents to find out." you said
'Maybe not. I only had the procedure that replaced my genitals a week after our parents left, they said I would need to report reporting on my experience with a male genitalia, as well as they do monthly checkups to make sure everything is okay, and also that the experiment would last 10 months, at the end of which they would reverse the process and give me my vagina back later if I wanted. So when our parents come back the procedure should have already been reversed." Sarah said