"Please let me lick your anus!!" I made such a request to a female university student who called out to me on the street. Female genitalia is obscene, but the anus is common to both men and women, so it's not obscene; it's just skin, no different from arms or legs. The feeling of it being indecent... is merely an overactive self-consciousness. Licking the anus is something that should be experienced while young!!
