Burikaesu Juusei. Caste Joui na Otoko no, 10-nengoshi no Gekiai

Reina was once a plain, unremarkable high school girl who fell hopelessly for Kuraki, a boy at the very top of the school's social hierarchy. When she finally gathered the courage to hand him a love letter, it was torn apart by the girls around him, and she was left with a broken heart and shattered confidence. Ten years later, she has transformed into a beautiful, successful career advisor who turns heads wherever she goes. One day, a man seeking job placement appears at her office, and to her shock it is none other than Kuraki himself. The brilliant student she once admired has become a five-year shut-in, his appearance and demeanor completely changed from the past. Yet when he looks at her, he proposes a startling bargain: if he lands a position at a major company, he wants one night with her. Reina is suspicious of his motives, but Kuraki's eyes are utterly serious. Behind his offer lies a shocking truth from ten years ago that has never been revealed. As he declares that he has always loved her, he showers her with ten years' worth of pent-up desire, caressing every inch of her body and drowning her in his fierce, obsessive love.

(Source: Suiseisha, translated)