Park Si-eun

Park Si-eun (박시은), known across the market as Sieun, entered STAYC with more camera mileage than most rookie idols ever get. Before the group debuted, she had already built a child-acting resume, moved through the JYP Entertainment system, and won the 2018 SBS Drama Awards' Best Young Actress prize for Still 17. That background matters because it explains why she reads so naturally on screen and in concept-driven performance.

Her next turn came after signing with High Up Entertainment in late 2019. When the Black Eyed Pilseung-built company launched STAYC in November 2020 with Star to a Young Culture, Sieun became part of the six-member lineup that gave the label its breakout act and helped prove a smaller producer-led company could still cut through the center of K-pop.

By 2026, that story had widened beyond debut nostalgia. STAYC had already pushed from early singles into full-project scale and a first Japanese studio album, while High Up's second girl group UNCHILD confirmed the label was building a real roster, not just one success. Sieun sits at the center of that first-wave foundation.