Oppai Heart: Kanojo wa Kedamono Hatsujouki!?

The main character Ryu and his younger sister seem to lead a normal life. They attend school, hang out with friends, and play soccer from time to time. In general, they do everything that ordinary teenagers of their age do.

However, fate sometimes brings unexpected turns. That's what happened to Ryu and his sister. They discovered a special drink that, as it turned out, can give girls enlarged breasts, and guys incredible strength.

But nothing in this world is easy. You have to pay a price for everything. And this is no exception. Anyone who drinks this drink gets a bonus in the form of an uncontrollable desire to make love. This desire will pass only after the girl becomes pregnant.

Ryu, as a gentleman, will not leave his sister Mia and other people who decided to try this insidious drink to the mercy of fate. He will do his best to heal them and help them overcome this ordeal.