Ai da, Koi dano Shouhosen

Destiny begins with the body - One day, Rinto Kiriya, a (β) and a pharmacist who runs a dispensing pharmacy, is asked to prescribe inhibitors to Shiro Sato, an (α) and a member of the popular band group Welt, by his entertainment agency. It turns out however, that when he meets Shiro for the first time, Rinto is filled with an intense lust, and he falls into Shiro's embrace. (Source: Ichijinsha, translated and edited)