Here is some extra info about the music video... Director Um Tae Hwa released a guide explaining the MV and gave 4 Key points.
First, the "cube" signified the discrimination and oppression that are prevalent in the daily lives of the main characters.
Second, the "camcorder" represents the "lens of love," an important "device" that allows us to look at the beautiful things in the world beyond the internal or external appearance of the characters.
Third, IU and BTS V became the main characters in a "survival story of a dystopian worldview of someone who cannot speak and sees the world only through his left eye." Despite the difficulty, feeling hurt and exhausted, they relied on each other despite "cube" and tried to overcome it in the end.
Fourth and last, the "wedding dress and tuxedo" symbolize the "fruit of love." At the end where their clothes are seen rising in the air, it depicts that they are finally "free to fly away from all kinds of oppression and pressure."
Have a wonderful day💜