DEY

On November 18, 2020, Sehyun was introduced as a member of the male trainee group BRANDNEWZ under Brand New Music. In 2021, he joined Mnet reality show High School Rapper 4 but was eliminated in the second round. On February 14, 2022, Sehyun, now known as DEY, was introduced as a member of the boy group YOUNITE.

They debuted on April 20, 2022 with the EP, Youni-Birth.