Sim Ja-yun

Sim Ja-yun (심자윤), better known as Yoon, is part of the STAYC lineup that turned High Up Entertainment from a promising producer play into a company with a real frontline act. She debuted with the group on November 12, 2020 through Star to a Young Culture, the release that gave the Black Eyed Pilseung camp a public-facing act to match its behind-the-scenes hitmaking reputation.

Yoon matters because STAYC's appeal has never come down to one gimmick. The group built its lane through melody, member contrast, and disciplined pop structure, and Yoon is part of the reason that mix feels vivid rather than interchangeable. As the catalog expanded beyond the first-hit phase, her name stayed tied to the project as it pushed from Korean singles into larger album cycles.

That arc was still growing in 2026. STAYC had already moved from Metamorphic into a first Japanese studio album, while junior group UNCHILD showed High Up was finally broadening its roster. Yoon's profile works best when it is framed inside that wider label expansion instead of treated like a generic member stub.