Kimekoi! Takane no Hana - Season 1

A drug known as "KimeKoi" is created to intensify any latent feelings of affection. Mukaiyama Hajime is deeply infatuated with Saginomiya Megumi, a student widely considered the most beautiful in school. Concerned she is beyond his reach, he seeks counsel from his friend Misa. Misa, who leads the science club, offers to help by producing the drug, but its formulation requires a sample of Hajime's semen. Hajime watches in confusion as Misa begins to unzip his pants.