I don't really get this. The other girls want to be friends with Yuu because she's so good looking that they can brag about it.
Okay, sure, doesn't really make any sense but whatever.
But going by that logic, why wouldn't they want to be friends with Umi? They haven't given any reason. Isn't she supposed to be almost as good looking as Yuu? (Very subjective opinion, but that's the freaking title of the manga). Wouldn't having two good looking friends be better for "bragging" than just one? Not to mention that Yuu and Umi are already seen as a package deal.
This really just feels like forced and artificial drama. Unless they don't want to be friends with Umi because of her personality. But then again they already established that they don't care about personality, only looks.
So far this doesn't make any sense. Maybe it will in the next chapters, but right now it just seems like the author is forcing Umi to be isolated so that her friendship with the "loner, loser, gloomy" Mc makes sense. There are better ways to do that though, but whatever 🙄