MBC's Friday-Saturday drama "21st Century Grand Lady" premiered on the 10th. This drama is set in the constitutional monarchy of South Korea in the 21st century and depicts the romance between a woman who is a chaebol but of commoner status and a man who is the king's son but has nothing.

IU plays Seong Hee-joo, the second daughter of Castle Group, who is about to marry Ian Daegun (Byun Woo-seok) in the drama. Seong Hee-joo is a nervous and calculating character who prioritizes her own interests. After agreeing to a contract marriage, when the public learns about their relationship, she says, "Marketing originally works best when it's very provocative or nasty," and adds, "Words like 'dating' are too bland; terms like 'hotel rendezvous' are more appropriate."

Last year, when it was announced that IU was cast as the female lead, "21st Century Grand Lady" attracted attention as a highly anticipated work. Along with Byun Woo-seok appearing as his next project after "Run, Seon-jae," there was also great interest in IU's acting transformation.

IU expressed Seong Hee-joo's lines in a charming way, portraying various emotions such as irritation, jealousy, stubbornness, and competitiveness transparently and honestly. IU revealed, "This is the first time I've acted so boldly upfront."

The viewership ratings started at 7.8% for the first episode and surpassed 10% by recording 11.1% in the fourth episode. She has been praised for skillfully portraying the chaebol character Seong Hee-joo, which is different from the Jeju girl Aesoon character she showed in last year's "I Was So Deceived."