[2] Sieun was well-known prior to debut as both the daughter of veteran singer Park Nam-jung, and for her roles in dramas such as The Good Wife, Queen for Seven Days, and The Crowned Clown.

[4] On September 8, it was announced that Black Eyed Pilseung of High Up Entertainment would debut their first girl group.

[6] The members were officially revealed in pairs via prologue films from October 12 to 14 (in order: Sieun, Isa, Seeun, J, Sumin, and Yoon).

The single album was announced to be produced by Black Eyed Pilseung, known for previous K-pop hits such as "TT", "Touch My Body", "Roller Coaster", and "Dumhdurum".

[13] On November 12, the music video for the album's lead single "So Bad" was released, receiving over 2.6 million views in the first 24 hours.

[16] On April 1, 2021, STAYC were featured in the YouTube Originals docuseries K-Pop Evolution documenting "their trainee days" and debut process".

[18] The music video of "ASAP" was released simultaneously with the album and reached 20 million views in nine days.

[37] On July 27, it was officially announced that STAYC would be embarking on their first world tour, also titled Teenfresh.

[39] On June 3, 2024, High Up Entertainment announced that STAYC's first studio album Metamorphic would be released on July 1, with the lead single titled "Cheeky Icy Thang".

[44] On February 10, 2025, it was announced that STAYC would be kicking off their second world tour, Stay Tuned, in Seoul on April 12 and 13, while a new album was confirmed to be released in March.