You and your friend Shukuro are camping in a woods, when both of you start arguing about something, during the argument, you both are abducted by a UFO

Next thing you know, both of you are in tubes

Aliens speaking

Alien1: Damn it, I thought you said it was a man and a woman.

Alien2: We wasted too much fuel on that tractor beam, let's just turn the bulkier one into a woman for bio-compost fuel.

You just so happen to be the bulkier one, while Shukuro is rather skinny and scrawny, both tubes fill up with a weird liquid, which both of you can breathe in.

Shukuro is bulked up in the water, becoming an absolute unit

Suction cups attach to your pecs and start vacuuming, and other various processes to turn you into a woman

When the process is complete, you pass out and fall onto the ground after the tube is opened, when you wake up, you're on a heart shaped bed, you're shocked to find yourself in the body of the ideal woman, but then look up and notice Shukuro towering over you, and it turns you on for some reason