Song Heejin

They debuted on August 30, 2017, with their first mini album All Day Good Day. Later that year, she became a contestant on KBS 2TV's reality survival show The Unit. She was eliminated in episode 13 after ranking 28th place.

GOOD DAY disbanded sometime in 2019. Since then, Heejin has moved onto being a music producer and lyricist as a member of a production group called Solcire in its studio Solcire Studio (now Solcire Music). Sometime in early 2020, Heejin was set to debut in the girl group REDSQUARE alongside former GOOD DAY bandmates Kim Jiwon, Kim Chaeyoung, Hwang Nayoon and Kim Yehyeon.

However she left prior to their debut. Her silhouette remains in various cuts of the music video. She was subsequently replaced by Lina.

Heejin's first works as a music producer began with the production of the mini album Layers for Ong Seong Wu which was released on March 25, 2020. On November 25, Heejin was featured in a collaboration duet song, titled "Alone In This World", released by Young K of DAY6. In March 2021, Heejin began a personal music production project to release music every Friday through her YouTube account.

The first song of the project, "GET OUTTA MY" was released on March 5. It was followed up with "Dirt", "Tylenol (3x A Day)", "Fly Like Butterflies", "Shade (Paint A Picture)", "Dancing In The Moonlight", "Question Mark" and a demo version of "Enough Just As You Are". Between March and May, Heejin was one of the lead producers and lyricists for the release of "Unnatural" for WJSN and "Surf" for TO1.

On June 1, Heejin announced the release of her first digital studio album, Soda. The album was officially released on June 10 and contains all the previously self-released songs she published on her YouTube with the addition of new track "Soda" and the full version of "Enough Just As You Are".