Kafun Shoujo Chuuihou! THE ANIMATION

Based on the manga by Koume Keito (小梅けいと). In this alter reality sex is not a reserved theme not even a discrete thing. Due to the existence of female and male pollinic humanoids, they travel just like pollen via the air and just when they find a receptive human they start their process of fertilization or at least thats what they intend to do...