Forever (약속) is the second digital single by aespa. It was released on February 5, 2021.
Forever is the remake of the same name song by Yoo Young Jin as a part of S.M. Entertainment’s holiday album “Winter Vacation in SMTOWN.com” in 2000.
The song is a mid-tempo ballad with an acoustic guitar sound and warm lyrics about promising forever to a loved one. It showcased showcase a different side of aespa, from their powerful debut song Black Mamba. Yoo Young Jin is said to have personally rearranged the song for the group.
On January 21, 2021, Cheon-hoon of Sonic Korea Mastering Studio teased aespa's comeback single, titled "Forever". The teaser was taken down a few hours after being posted.
On January 29, 2021, aespa's official Twitter account promoted the hashtag #늘_네_옆에_난_서있을게 (#I_will_always_stand_by_your_side). It was later revealed that the group would release the single "Forever" on February 5.
Concept photos were released on February 1 to February 4.
On February 4, 2021, SM made a statement stating that aespa will be releasing three performance videos that show a variety of concepts on the 6th, 8th, and 10th. A couple hours later, the M/V teaser for “Forever” was released on SMTOWN’s YouTube channel.