On... a beach?

"Ren..."

...Ugh, what happened? Why does my head hurt so much?" You think to yourself blearily. "Why does my bed feel so gritty?"

"Ren...!"

You can feel the sun on your face. Gah, did you forget to close the drapes again? What time is it? ...Is that water you're hearing?

"Ren!"

Your eyes snap open as you bolt upright, the memories flooding back to you. This isn't your bedroom. As far as you can tell with your still blurry eyesight, you were on some sort of... tropic beach? And sitting in front of you was Yu Takeyama... Mt. Lady.

"Ah! You're awake!" She says, sounding pleased. "I was worried you were done for. That would've sucked. Although a 'steak' doesn't sound to bad, given our current circumstance..." She trails off, her smile fading.

"Yu... where are we? What happened?" You manage to croak out groggily. She sighs. "I regained consciousness just in time to see that guy knock you out. After that, this weird gray stuff started pouring from all three of our mouths, and suddenly, me and you were here." Shifting uncomfortably, she adds; "Also... There is a backpack. It's got a note that kinda explains what's going on."

"Okay. Show me. And how's your head?" You ask shakily, as you attempt to stand up before collapsing. "Whoa whoa whoa! Let's get you acclimated before you take any more shock! Can't have you going catatonic again!" She protests, as she helps you up and leads you to the water. "My head's fine. Here, just... splash some water on your face? Get cooled down? Do some jumping jacks? I never was good at this sort of thing..." She mutters.

As you wash your face, your eyes become more used to the sun. Wiping your face off, you catch a glimpse of your reflection in the water and gasp. Were those tiny nubs... your horns? And did your cow-like ears shrink? As you flick your tail anxiously, you feel something else wrong! Your tail! It too has shrunk, and feels far weaker. Similarly, the rest of your cow like traits have began to lessen. It seems all that remain in their original form are your muscles, which thankfully appear to be intact, more or less.

Noticing your distraught expression, Yu offers a comforting shoulder squeeze. "Ren, I'm sorry. A-about whatever's wr-rong with your quirk, I-I mean." Her voices wavers. As you turn to face her, you finally get your first clear look at her since your awakening. What you see shocks you.

Yu still only wears her special, size changing, cream colored bra and panties, as they were the only clothes she had on her when she was teleported, but, like you, her body has changed dramatically. The first thing you notice is her figure. Her breasts have grown dramatically, with each one easily dwarfing her head. Additionally, her thighs and ass have also filled out slightly, as though attempting to maintain some kind of balance. Luckily, her size changing garments are designed to stretch, so her new proportions are accommodated comfortably.

The most prominent changes, however, are the presence of a small pair of horns now adorning her head (though, they are larger than your current pair of nubs), and the small tail swishing back and forth behind her. It looks like you're not the only one who's body is changing.

Yu finally breaks down in tears, having clearly been holding them for your sake. "I-I'm turning into some kind of monster-r-r! Waaaaaah!" She bawls, burying her face in your chest as she hugs you. As her breasts press against you, you guiltily begin to feel a little turned on.

As you hold her in your arms, comforting her, you wonder what's wrong with you bodies. Those horns, that tail... they aren't unlike your own.