A special Aphrodisiac that has been passed down for generations back in a certain hentai doujin that Haru Doi has read before. It's also known as Desire Drive and Daoi.
It can attract any girl to the user, ignoring entirely their sexuality (meanwhile a male can attract homosexual females with the Bisui), aleast according to Haru. (He happened to be wrong.)
There are three types of Bisui: The main one, one that attracts yuris (lesbians) with their (possible) crushes and one that's for bisexual.
It is unknown if the main bisui works on homosexual females if used by a guy