The behind-the-scenes story of IU wearing a school uniform and playing a 16-year-old character was revealed.

On the 14th, the YouTube channel 'Lee Ji-geum' uploaded a video titled "I Still Want More (Identity) | Behind the Scenes of 21st Century Great Lady." In the video, IU introduced the role by saying, "I am Seong Hee-joo, a 9th grader at Jusakgung." Then, before acting as a 9th grader, sixteen years old, IU laughed and said, "It's a bit of a stretch," and explained, "I asked the director and writer, 'Wouldn't it be better to cast a child actor?' but they said, 'The child actor's scenes are few and important, so we want you to do it,' so I ended up doing it."

In the released video, IU appeared transformed into 16-year-old Seong Hee-joo wearing a school uniform. Despite being 32 years old, IU naturally pulled off the school uniform look, attracting attention.

Meanwhile, '21st Century Great Lady,' which premiered on the 10th, recorded an 8.2% viewership rating in the metropolitan area and 7.8% nationwide, ranking first among Friday-Saturday dramas.