IU is playing the role of Seong Hee-joo in MBC's Friday-Saturday drama '21st Century Great Lady,' leading the latter part of the storyline.

In episodes 9 and 10, aired on the 8th and 9th, Seong Hee-joo's emotional depth deepened following the leak of the marriage contract, and the changes in her relationship with Prince Ian were fully portrayed. IU expressed a range of emotions including inner turmoil, resolute determination, and tender love, enhancing the drama's immersion.

In the drama, Seong Hee-joo showed a strong will not to waver despite the complicated situation after the marriage contract leak. In her conversation with Queen Dowager Yoon I-rang, she maintained a calm demeanor, but Yoon I-rang's words that Prince Ian's downfall was her fault lingered in her mind, depicting a scene where she struggled to steady her heart.

Additionally, Seong Hee-joo expressed desperation and sorrow in a scene where she knelt before her father, Seong Hyun-guk, asking for help. After returning to the palace, she showed a cold attitude while hiding her true feelings, saying "Let's get a divorce" as she was embraced by Prince Ian.

Later, Seong Hee-joo declared the divorce herself to take all the blame upon herself. After Prince Ian disappeared, she searched for him and confessed her feelings by saying "I like you" when they reunited, revealing her true heart. The kissing scene that followed, where the two confirmed their feelings for each other, depicted emotions filled with both excitement and sorrow.

In the scene where Prince Ian revealed his feelings about the throne, Seong Hee-joo conveyed both a resolute attitude to stay by his side and comfort. Toward the end of the drama, a fire breaks out in the royal chamber, and upon learning that Prince Ian is inside, Seong Hee-joo is shown panicking.

'21st Century Great Lady' is a drama set in the 21st-century constitutional monarchy of South Korea, depicting a romance that breaks social status barriers between a chaebol woman of commoner status and a prince who has nothing despite being the king's son. The cast includes IU, Byun Woo-seok, Gong Seung-yeon, Noh Sang-hyun, Lee Yeon, and Yoo Soo-bin, with only two episodes remaining until the finale.