The President's Alternate Bride

After her elder sister eloped with another man the day before her wedding, she was married off to her elder sister's enraged groom-to-be. On the night of their wedding, her handsome but distant groom ordered her to "start fulfilling her duties as his wife", only to call her by her elder sister's name even after she'd relented and shed her clothes for him...She had no idea that there was much to come than simply replacing her elder sister as the president's alternate bride...