Oppai Heart: Kanojo wa Kedamono Hatsujouki!?

Ryuya has an older sister, Miya. He lives a peaceful school life with his friends. But one day, he and his friends accidentally drink a medicine juice. Once you drink it, you'll become sexually sensitive and get excited. The breasts of the girls who drink it will get bigger and they will need to have sex to cool down. Also, to make a vaccine, they...