Okay, I'll tell you why this sentence actually works for me:
It's dirty and yet not inelegant. "Rosy" is a cute, cliched word, even a little childish that way. When I know that it's being used to describe something so forbidden and sexual, it makes me blush. "Pucker" has very much the same effect--it should be a neutral word and yet when it's said, I know exactly what you're describing, so I'm feeling supremely naughty by that point. "Untried"--you're telling me that he's a virgin without using the obvious word or spelling it out in unsubtle, agonizing detail, and that gives me a pleasurable feel. (Not to mention my Virgin kink.) And "entrance" is the word that's chosen to end it, on a gentle euphemism, so that the feeling of blushing naughtiness is given a moment of justification: "It's all right to like this dirty stuff." I like this phrase. If it fits into the rest of the language of the text I wouldn't have any trouble with it.
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It's dirty and yet not inelegant. "Rosy" is a cute, cliched word, even a little childish that way. When I know that it's being used to describe something so forbidden and sexual, it makes me blush. "Pucker" has very much the same effect--it should be a neutral word and yet when it's said, I know exactly what you're describing, so I'm feeling supremely naughty by that point. "Untried"--you're telling me that he's a virgin without using the obvious word or spelling it out in unsubtle, agonizing detail, and that gives me a pleasurable feel. (Not to mention my Virgin kink.) And "entrance" is the word that's chosen to end it, on a gentle euphemism, so that the feeling of blushing naughtiness is given a moment of justification: "It's all right to like this dirty stuff." I like this phrase. If it fits into the rest of the language of the text I wouldn't have any trouble with it.