In episode 5 of MBC's Friday-Saturday drama "21st Century Great Lady," a scene aired where Prince Ian (played by Byun Woo-seok) declares the cancellation of his engagement to Sung Hee-joo (IU). In this episode, as Sung Hee-joo and Prince Ian were moving forward with a contract marriage, their trust and feelings for each other deepened, but an unexpected conflict arose.

In the drama, Sung Hee-joo experienced a car accident, and Prince Ian was injured while protecting her. Afterwards, Prince Ian expelled Sung Hee-joo from his residence. Sung Hee-joo left a message for Prince Ian saying, "Let's meet and talk. Whatever it is," but Prince Ian responded, "Someone tampered with your car. That's why the accident happened. It's under investigation. We will catch them. So, I have to change the plan. Let's call off the marriage," notifying her of the broken engagement. Sung Hee-joo protested her innocence, but Prince Ian added, "If I marry someone with as many enemies as you, the royal family won't survive."

It was revealed that Prince Ian's rejection of Sung Hee-joo was rooted in trauma from losing his mother in a past car accident. When Choi Hyun (played by Choi Hyun-jin) asked him the reason for the broken engagement, he thought to himself, "I'm afraid she might die."

Meanwhile, Sung Hee-joo instructed Do Hye-jung (played by Lee Yeon) to "thoroughly investigate everything from A to Z about the last person who touched my car." Additionally, Min Jung-woo (played by Noh Sang-hyun) revealed in a conversation with Yoon Yi-rang (played by Gong Seung-yeon) that "It's about protecting the royal family," exposing internal conflicts within the royal household.

The episode also showed Sung Hee-joo and Prince Ian sitting across from each other in a cold atmosphere, confronting one another. A scene where Sung Hee-joo aims a verbal attack at Prince Ian was also featured. Attention was drawn to how their conflict would unfold.