Megaria21 | 이서연

Aktor · Lahir 2000 · Seoul, South Korea

Megaria21 | Lee Seo-yeon, known professionally as Y:SY, is a South Korean singer-songwriter and rapper under H1GHR Music. She is a former member of the girl group fromis_9, formed through the reality survival show Idol School (2017). She left the group in 2024. She made her solo debut on November 17, 2025, with the digital single Naked.