With the deftest of ease, Mom removes her shirt, removes the other, creme-colored bra she had on, and hooks you behind her back. "I was thinking about switching our bodies," she says as she goes about adjusting you so that the edges of your cups are fully aligned with her breasts, not folded in anywhere or puffing out, "and making you be me, but truthfully, much as I would have enjoyed the reversal of fortunes and the chance to be a devil-may-care teenager, I also wouldn't have felt comfortable giving you my life, with its job and responsibilities and honor. You're much better as a bra, believe me."
There's no way for you to protest, or to scream, "Change me back!" All you can do is mentally grimace as you stretch out the full length required to go around your mom's body, your "arms" joined together and your "back" / "torso" / "face" pinned to her breasts, subject to their every heave, given nothing for the hard labor of keeping them in place except sweat stains and maybe a rip somewhere down the road.
"It should also go without saying," your Mom says, striking a confident, Maxim-cover pose in the mirror, "that you're never going to be human again. A bra is what you'll be forever. Good news about that is bras don't die like humans do. I can fix you and make you good as new once you start to wear out, and I'll switch up your design so that you always stay fresh, but otherwise, you won't be subject to the same laws of aging as me. You should be proud: I've given you the secret to immortality."
"Forgive me," you think, bitterly, "if I'm not rushing to thank you."
Mom stretches her arms above her hand, sighs merrily, and walks out of the bathroom, shirt still off, giving you a full view of the world from Mother's bosom. Her breasts quaver a little with each step; your vision, when she's in motion, is a seasick blur, almost nausea-inducing except there's no longer anything in you physically that can experience nausea. It's only a vestigial layover from your old human life, occurring entirely inside your thoughts. Mom falls face-first onto the bed, and as you swing down towards the mattress, you're terrified that the impact will kill you... But no. Despite being crushed between the weight of your mom and the bed, nothing happens but the world goes dark for a moment, Mom's breasts get squished against you, and you're rubbed between her flesh and the bed's fabric for a few seconds before Mom gets up again, wiping you up and giggling.
"Must have scared the shit out of you, didn't it?" Mom says. "That's the other thing, too. You can't be hurt as a bra. If I tear you in half, your mind will be split between the two pieces, but otherwise, you won't ever feel pain the way you did as a human being. Isn't that wonderful too, huh?"
"Now," your mom goes on, "what can I do to have fun with you now? Hmm..."