Kimekoi! Takane no Hana 1

Just one pill and you can't stop!! It's a drug that helps people realize their true love. This aphrodisiac unites a "beauty beyond reach" with her childhood friend, and passionate sex ensues! Mukaiyama Hajime falls hopelessly in love with the student rumored to be the most beautiful in school, Saginomiya Megumi. He plans to confess his love to her but worries that she's out of his league. He asks his friend Misa for advice.

Misa, president of the science club, develops "KimeKoi", a drug designed to amplify any preexisting feelings of affection within the user. But a sample of Hajime's semen is needed to make the drug. Hajime watches, bewildered, as Misa starts unzipping Hjime's pants...