Boku wa Ayashii Kimi no Mono

Shou-chan is a member of the public morals committee who wants everyone to have a healthy relationship, and is worried about his childhood friend Sayo. Because she carries the blood of a succubus, she often approaches her beloved her Shou-chan in any way to do "lovey-dovey sex." As he persists in having a healthy relationship, which is full of lust and surrounded by questionable students, will Shou-chan manage to keep his sanity?

(Source: Kodansha, translated)