The Countess is a Male Omega

There is only one condition for the contract: To fulfill the duties of the Countess of Meyer. In exchange, the family's debts will be cleared, and he will receive five hundred million in cash to support his younger siblings. "...I'll do it." After all, isn't he just marrying an old man who will be dead soon? Though he doesn't know why they sought out someone like him—a male Omega—of all people. Thus, Gabriel decides to become the Countess of Meyer and enters the Meyer estate... What is the true condition that awaits Gabriel?