'Chuhai Lips In the Aftermath of Yui Koriyama' is effectively Episode 9 of Chuhai Lips, but with two small differences: 1) It's listed separately as a special episode, and 2) a follow-up of Episode 1, which deals with Tsuyoshi's aunt-in-law, the same woman in the key visual of this special and the ONA. I give this special a rating of 4 out of 10 as this is part of the Chuhai Lips ONA, including its weaknesses: 1) it only introduces different types of married women, but it does not care to deepen its story, and 2) it is not for everybody. This satisfies a youngguy's fantasy, but it can potentially raise anxiety for married men.
A further weakness of this special is that it shows the silly rationalisations of both men and women regarding sex. Without spoiling what it is specifically, let's just say it's something similar to the idea that as long as the penis does not penetrate the woman's vagina, she remains a virgin even if you let her suck your dick or you fuck her butt.
Despite being on the lowest end of my enjoyment scale, it is slightly better than the main series, which is why I am marking it as recommended.
Firstly, it's likely that you find Yui either as your best girl or at least near the top. Thus, she is the logickal choice for a follow-up episode.
Secondly, it follows up and deepens Tsuyoshi's relationship with Yui. It's the closest thing we can have to character development.
Finally, the shots of Yui's breasts are better here.
NOTA BENE: A grade of 4 out of 10 means I got some enjoyment out of this anime, but the issues are glaring, or simply I rank it higher than my 3's but below my 5's.
My enjoyment spectrum lies from 4 to 10. If I have scored an anime below 4, I actively dislike it.