You Dayeon

You Dayeon was first introduced as a member of LIPBUBBLE under the stage name Seoryn on December 22, 2016. She officially debuted in the group on March 22, 2017, with the group's first digital single "Popcorn". She left the group in Spring of 2019 and later joined the dance studio 1MILLION.

On July 7, 2021, she was confirmed as a contestant on Mnet's newest reality show Girls Planet 999, along with the other participating trainees, through the prologue trailer. In the fifth episode, which was aired on September 3, it was revealed that Dayeon, along with her cellmates, was unfortunately eliminated. On October 15, 2023, she announced that she will make her solo debut with the digital single (labeled as a single album) "Down Down Down" on October 20, under Dot Music.