Back when I didn't know any better

[Chinese Drama Cliché☆] Jiyoon leaves behind Sehun, a CEO of a major corporation who has only eyes for her, and falls for and marries Taehyun, a nameless CEO of an unknown company. Eventually, she is killed by him and the woman he truly loved, and returns to five years in the past; at that point, it is already the day before Jiyoon spoke harshly to Sehun and was about to marry Taehyun.