Lilith staggered up the stairs in her last body-expanding destination, her friend Eliza’s house. Lilith’s tremendous bust swayed back and forth as she walked, the basketball-sized masses blocking any view of her torso. She had believed that she didn’t want to get back to her original bust size—the basketball boobs that her mother had stolen—but as her friends surprisingly kept volunteering some or all of their breast mass for her, Lilith discovered that she felt wrong without her tits dominating her figure.

Eliza had come to her with a different kind of volunteering.  Eliza was undoubtedly busty- but that’s not what she wanted to lose. No, Eliza wanted to see if she could donate some of her hefty butt to Lilith. For her part, Lilith was excited to see if the tape could transfer things other than boobs, and having a bigger butt to help balance out her chest behemoths wouldn’t hurt.

“I hope you brought some yoga pants,” Eliza said, “I want to be completely top-heavy.” Her bountiful H cups would make that easy once Lilith had her butt. Eliza’s ass dwarfed her breasts in comparison. Her butt cheeks were like two volleyballs, supported by hips a foot and a half wide. Lilith pulled her jeans off—so she didn’t have to worry about her butt having enough room to grow—and kneeled in front of Eliza and wrapped the tape measure around Eliza’s butt.

“I did, but I might have to borrow some of yours, if I’m taking this entire ass.” She pulled. Will this work? She thought. Her arms didn’t encounter resistance as she pulled the tape tighter, so she guessed it did.

“Please, take all of it. I’m sick of having a giant butt.”

Lilith could feel a tingling sensation as her already large rear began to expand with Eliza’s contribution. It was harder for her to visualize than her boobs growing because she couldn’t directly look at her butt. What she could do, however, was observe the diminishing size of Eliza’s and think about adding that on to what her butt used to look like.

As her butt pushed out further and further, forming a bubble butt that would put most other girls to shame, the expanding felt just as good as her tits did. She could feel her hips widening as she kept tightening the tape around her friend.

“I’m really glad I took my jeans off for this,” Lilith said, laughing, “They’d be killing me by now. Your butt was gigantic, girl.”

Eliza leaned over slightly, trying to get a good look at Lilith’s posterior. “Looks like yours is now, though. How much more is there?”

“Just a little bit more.” The sensations were coming to a head, just like when she expanded her boobs. Lilith could feel a climax coming on. “Oh, ohhh, OH, not- oooohhh- again.”

She came, jerking her arms tighter, taking the last of Eliza’s ass in one swift motion. Her hips widened and her own butt ballooned out behind her, the cheeks almost rivaling her tits for size.

“That’s it, Eliza. Now you’re officially top heavy,” she said, “And I,” she continued, looking into her friend’s full length mirror, “Am incredibly sexy.”

“I’m glad you’re happy, Miss Curves-For-Days,” Eliza sassed.

Lilith pulled on a pair of Eliza’s stretchy black yoga pants. Her huge ass barely fit into them. “I think I need something to eat after that. How do you feel about milkshakes?”