It was a little late at night and you walked back into your dad's lab. You thought that some experimenting with your dad's things should be done in his lab. However as you was approaching the door you heard your 13 year old sister Erin mumbling something and then opened the door. You saw your sister in all her brilliance, but with her breasts at the size of basketballs and lactating milk. You saw that her shirt hadn't actually burst open and that her nipples probably were pointed to the floor.
She said "I can explain! I wanted to see if you had messed with any of dad's stuff in here and I hit some button and I was hit with a ray and now this has happened..."
you said "I kind of want to do some experiments with something I had found here. I wont tell about your breasts if you'll agree to an experiment or two... then we can fix your condition. Mom's asleep after all and we've got hours."
Erin sighed and said "fine... let's just make it quick... what are you even doing?"
you said "It swaps body parts of different of the same people..." you may want to take your shirt off." Your sister took her shirt off letting her breasts flop and a snapped bra fell. You then selected your sister on the tablet and touched one of her breasts and then the other switching the two.
Your sister looked at her chest feeling something odd and asked "what did you do?"
"this was an example of what I can do... I made your left breast your right breast and your right breast your left breast." you felt yourself get hard and then said "of course I can swap body parts such as..." you tap your dick and then tap your sisters pussy and then felt an emptiness in your crotch, but you saw you sister's expression as her panties felt tight. She pulled down her skirt and then saw your hard dick on her crotch. You notice that it was dripping with pre-cum and think that she must be pretty horny and sensitive thanks to the hard dick and lactating breasts. You poke your sister's pussy a little and found it to be a little sensitive, but said "However I think I prefer my dick so..." you tap your sister's dick and your pussy and they returned to their normal locations. you decide to show her one other feature and said "one last thing to show you before the experiments." You walk over behind her and hand her the tablet and said "here is something interesting I found out the hard way." you tap and hold on your head and tap and hold on your sister's head, and then the switch occurred. You look down and saw you were now holding the tablet with some girly hands and that you had some really large breasts that you could feel the milk dripping out of. You said "wow these things are sensitive... anyways if you tap and hold on a person's head you select their brain. Basically we just traded minds or in other words traded bodies."
Erin said through your mouth "Alright then... Now give me back my body and let's go ahead with your experiment... how about one experiment of yours for every solution we try for me."
You nodded and said "Yeah." as you switch your bodies back. You then quickly snatched the tablet back with your greater strength and then start with your experiment. What did you do though?