Songfacts®:

• This chilly ballad finds Lauv addressing his lover. She has changed, and he doesn't recognize her as the girl he once fell in love with. Lauv is joined halfway through the song by BTS singers Jimin and Jungkook. The pair has also grown apart from their lady, who they accuse of lying. At the end of the song, the three conclude that their romantic partner is not "the one" anymore.
• Lauv first met BTS at their Wembley Stadium, London concert during which the group asked him to contribute a verse for their "Make It Right" remix. Lauv explained in a How I'm Feeling playback that after the remix successfully came together, he sent a song that would eventually become "Who" to BTS. He had no expectations that the boy band would agree, but after a "very cool, very interesting, very mysterious" process of sending vocals back and forth, they came up together with an "epic" emotional track.
• Lauv wrote the song with Zaylee Kelman and Why Don't We boyband members Corbyn Besson, Jonah Marais and Daniel Seavey.
• Los Angeles native DallasK produced the track with Lauv. DallasK also co-wrote and co-produced Lauv's single "Sad Forever."