Shin Seo Yun

Sometime in 2020, Seoyoon joined AMX Entertainment as a trainee. She eventually became a trainee of their pre-debut team AMX Trainee (also known as 'AMX NEWKIDS'), however on July 29, 2021, it was announced that Seoyoon's contract with the agency had been terminated. On May 12, 2023, she was revealed as a member of the pre-debut group SPIA.

She eventually made her official debut with the girl group SPIA on April 2, 2024 with the release of their digital single "Daddy's Little Girl". On May 22, 2025, HUX Entertainment announced they signed with Sera who will now go by her birth name Shin Seo Yun.