[#] (read as "hash") is the second extended play by South Korean girl group Loona.

The clip looks back to Loona's previous releases and teaser films and ends with the word "burn".

On May 31, a second teaser was released titled "La Maison Loona", with the phrase "delayed but someday" showed at the end.

[4] On January 8, 2020, it was announced that member HaSeul would halt activities with the group due to health concerns.

[10] The description of the "So What" music video announced that the album's limited editions included a CD-only song, "Day & Night".