Myung Hyung-seo (명형서), known professionally as HYUNGSEO, is a lead vocalist and visual member of CLASSy. She joined the seven-member group after appearing on MBC’s My Teenage Girl and made her CLASS:y debut on May 5, 2022.

Unlike several of her fellow members, HYUNGSEO had already worked in the music industry before the competition: she previously performed with Busters. That experience gave her an earlier introduction to recording, choreography and live appearances. Within CLASSy, her clear singing voice and measured delivery complement the group’s more energetic performance style.

The June 2026 EP RE:BOOT [AFTER TEARS] brought a new opportunity for individual expression. HYUNGSEO performs On My Way, a solo song included in the group’s nine-track release, and also contributed writing to the project. An official performance clip puts her voice at the centre of the arrangement. The recording is a member solo track, rather than a separately released solo album.