Oppai Heart: Kanojo wa Kedamono Hatsujouki!?  

젖가슴하트 ~그녀는 짐승발정기~, おっぱいハート~彼女はケダモノ発情期ッ!?~, おっぱいハート～彼女はケダモノ発情期ッ!?～

Ryuya has an older sister named miya. he leads a tranquil school life alongside his friends. however, one day, he and his companions accidentally consume a medicine juice that causes increased sexual sensitivity and excitement. as a result of consuming this drink, the girls' breasts will grow larger, necessitating them to engage in sexual activity to alleviate their heightened emotions. in order to create a vaccine for this affliction, the individuals must become pregnant. due to these circumstances, ryuya initiates romantic relationships with the affected girls in an attempt to cool them down and produce offspring for the purpose of creating a cure.