This is a bit of a spoiler, but it may prepare you for a little shock.

Of course, I can't read Korean, but luckily IU's unofficial/official English translator shared a few bits on her Twitter. Thanks, squishy!

23 year old Cindy's (IU's character stage name) real name is Jo In Yeong
Cindy feels that her position is threatened by junior idols and decides to go sexy and wear see-through!

Music Bank PD, Yejin, tells the junior idols to bring Cindy a jacket for the recording, but the moment the song starts, she takes off her jacket revealing her see through outfit and doing a choreo in it, to the delight of the audience, but leaving Yejin flustered.

photo source: link

trans source: link and her TwitLonger link