ボクの精子がグラビアアイドル志望女子のおっぱいを膨らませる特効薬だった件

Rio is on track to become one of the best in the entertainment business. She has one hurdle: her washboard chest. The answer is in... the protagonist's balls!? His (your) semen is a miracle seed that grows little tomatoes into juicy melons. [From DLsite English]