Source? Even though that girl on the ground's probably just a side character, with the female lead being lolicon bait or something.
Naturally, this author--who favors androgyny--would do something like this. He has Yuria, a busty beauty, get together with Almus (in no higher a position than second, because he doesn't like busty girls). Then he introduces another that's bustier than Yuria, has Almus oogle her with his wife right next to him (Almus just keeps scoring with his newly wedded wife; imagine the flatchest being there instead of Yuria), and even nerfs Yuria's bust massively to drive the point home.
A lot of authors do this sort of thing; they introduce a beautiful female lead, then introduce someone that's explicitly intended to overshadow the femald lead. Misora Riku did the same with his Rakudai Kishi no Eiyuutan. Absurd--a story's female lead should be tops in her design, the same way a male MC should be the coolest character in the cast (or, at the very least, should not be completely overshadowed in that regard).
I suppose the difference here is that this author did not intend to have Yuria be the female lead in the first place--and, instead, actually intends for Yuria to be the object of at least subconscious contempt in the reader's mind.