Shiru o Kakerareru Shoujo ~Yarisute Gomen!? Seieki de Kioku o Kesu Otoko~

I'm Akashi. The other day, my father suddenly told me, "You must get married soon after you graduate from school. I've already selected three fiancees for you. The girl you have sex with first will be your wife. That's all." Oh, my.... What? A parcel to me? What's this...? A new medicine? "I've invented a new medicine with which you can get an ability to erase other people's memory...." Oh, great! With this medicine, I'll be able to have sex with all three girls! Thank you!