One song in the album, "Only I Didn't Know", appears twice – the second time as a collaboration piece with pianist Kim Gwang-min.

[2] The music video for the lead track, "Only I Didn't Know" (Korean: 나만 몰랐던 이야기; RR: Naman Mollatdeon Iyagi), features actress Park Bo-young as she is caught in a dramatic break-up story.

Her ex-lover is played by singer-songwriter Yoon Sang, who also composed this piece as a gift for IU.

It features a mature combination of IU's striking high notes, vocals and orchestral instrumentation.

[4] IU made her promotional comeback with "Only I Didn't Know" in the television show Music Bank (KBS) on February 18, 2011, two days after the album's release.