Copipe!

Miku and her younger brother Yukito become the test subjects of their older sister's latest invention: a mysterious gel called "copipe," which has the power to copy and transfer body parts between people. When Yukito suddenly gains a copy of Miku's breasts, and Miku receives a corresponding change, their everyday life is thrown into bizarre and erotic chaos.

As the siblings struggle to cope with their swapped anatomy, their older sister watches with scientific curiosity—and perhaps a bit of mischief. The gel's effects lead to increasingly intimate and awkward situations, blurring the lines between family and desire. Soon, everyone involved finds themselves taking advantage of this strange phenomenon, and unexpected feelings begin to surface amidst the pandemonium.