Pine Tree; stylized in allcaps)[4] was a South Korean girl group formed by TS Entertainment.

The album presented a new side of the group with a brighter "girls next door" image compared to their debut concepts which the members themselves called "dark".

The lead single of the same name is a brighter dance track produced by Shin Hyuk, who has previously worked with SHINee and EXO.

[12] On July 27, TS Entertainment unveiled a teaser image for Sonamoo's Happy Box Project, revealing that the group will be releasing three singles over the course of several months.

[13][14][15] Member Euijin was confirmed to be a contestant on KBS Idol Rebooting Project The Unit, which first aired on October 28, 2017.

[18][19] In January 2021, Sonamoo's label, TS Entertainment, privately shut down and deleted its website, leaving the fate of the group unknown.