Makemasen kara to Iiharu Kao no Ii Onnanoko wo, Zenryoku de Kuppuku saseru Yuri no Ohanashi

Sara Kureha is the reigning "Super Onee-sama" of an elite ladies' academy, a position she's earned through nothing but relentless effort. Her status is suddenly challenged by Rui Mareshino, an effortlessly perfect beauty who proposes a secret contest to determine who is truly fit to get on top. With the school-wide popularity poll just two months away, they need a way to settle the score, just the two of them. Rui's method is... quite unexpected.

"So, that's why... you're going to be my girlfriend."
"Huh...?"

The rules of their new relationship are simple: the first one to make the other completely submit proves she is worthy of ruling the school! And so begins a secret war of seduction, with each girl launching an all-out offensive to make the other fall for them first. In this heated battle, whose heart—and body—will be the first to surrender? And who will be the one to conquer them? Prepare to be dominated by this romantic comedy showdown between two pretty girls!

(Source: Shueisha, translated)