Daddy's Bride, Billionaire's Game Manga

On her wedding day, Katherine discovers that her groom is marrying someone else. Betrayed by her husband's family and her best friend, and left drowning in debt, she hits rock bottom. Then, an old man appears, offering a huge bride price to marry her. Amid public ridicule, he summons his powerful grandson, Jonny, who marries Katherine instead. Jonny assumes she's a gold digger fooling an old man, so he hides his true billionaire identity. But as they grow closer, he slowly finds himself drawn to the woman he misjudged.