two enormous busty beauties have a grow off to see who has the strongest, largest heart
"I'm totally bigger." They kept saying over and over to each other, trying to prove that they were the biggest, sexiest, curviest, most buxom babe around, with the largest heart too. Their heartbeats made it hard to predict who was really bigger despite their very audible sound, since their heartbeats had synced (perhaps in love~), meaning they made only one, very strong, continuous noise that was on the same 'volume' as their voices as they boasted to one another.
They squeezed their gigantic tits in their tight bikini tops, letting their hearts make all the bouncing, and also shook their hips from side to side, flaunting their beautiful bodies to each other and anyone who could be watching their growth competition.
Occasionally, they'd mismatch in their growths, which would cause them to argue less objectively. One of them would get taller, and get wider hips while the other remained clearly bustier, with a canyon of cleavage that outsized the other's bosom hills. Since that was a lot harder to compare, and they wanted to be bigger at EVERYTHING, they settled...to only compare their hearts, which they could feel were dozens of times larger and stronger than they were when they started, let alone compared to a regular person! They were basically curvaceous goddesses fighting to outgrow each other, pressing their chests against one another, trying to feel each other's heartbeats from up close to see whose was stronger...
Eventually, getting that close and intimate while so aroused might have led to kisses, idle growth, and less interest in competition and more in...'cooperation', if you get what I mean~ <3