My best times learning Korean (at super basic level 0.01) was with a great Korean speaker friend Andy Kim (korean roots, American, lived in South America). I learnt words from the barbeque table like water (mul), mulbyeong, bul (fire), and also IU. I had heard about IU a little, until he told me she is the Korean people's little sister and in Korean is 국민조카 - (translated as national niece/nephew) - gugminjokha; and she was able to sing very well and even at the crescendo (of high notes), she can do a progressive push 3 notes upwards.
Then I went back and watched the Youtube video and yes: she does it - effortlessly. (no strain in facial expression, as in most singers who are singer top of their lungs or notes, they will cringe showing much effort)
So finally now I can read some Korean words and here was the "nation's little sister" from a short skit of the Running Man TV program. IU was singing to wake up the participants on a presumably very cold winter morning. That means she woke up way ahead, prepared studio stuff (make-up etc) and mock as a singing bird to wake them. What fortunate luck those goons!