I Bought His Love, Then He Became the Don

Here is a short English synopsis for the script:

In college, Vivian, a wealthy and overweight heiress, "buys" the affection of Roman, a brilliant but destitute student, by paying for his grandfather's surgery. Believing Roman only stays out of obligation, Vivian breaks up with him when her family goes bankrupt and completely vanishes. Five years later, a drastically thinner and impoverished Vivian crosses paths with Roman, who is now a ruthless Mafia Don.

Roman, who had actually loved her all along, descended into the criminal underworld solely to build the power and resources needed to find her. After clearing her family's dangerous debts and violently dismantling her enemies, Roman finally reveals the truth: he never saw himself as her "toy," and his terrifying empire was built for her. The two clear their painful misunderstandings and reunite, their love stronger than ever.