STAYC’s Sieun touched hearts with a sentimental and emotional stage.

On the December 2 broadcast of Mnet’s Steel Heart Club, Sieun delivered a special collaboration performance with the Hanbin Kim team.

Ahead of the Round 4 Part 2 “Collaboration Unit Battle,” Sieun met with the Hanbin Kim team (Kim Jiho, Nam Seunghyun, Park Hyungbin, Sagisomul, Seo Wooseung, Shin Jaemin, Jung Eunchan, and Hanbin Kim). The atmosphere instantly heated up the moment Sieun appeared, and Sagisomul shared his excitement, saying, “I used to always watch STAYC on TV during my time in the Marine Corps, so it felt like a dream.”

With Sieun joining, the team gained strong mainstream appeal. When asked to share her secrets for winning fans’ hearts with a “steel heart,” Sieun mentioned gestures like winks and hand-kisses, and even taught them the iconic “kneading dance” from “ASAP.” Leading the mood with ease, she suggested performing Younha’s “Event Horizon,” noting its lyrical and emotional qualities. The Hanbin Kim team agreed, saying it would allow them to show a new side of themselves.

Sieun worked closely with Sagisomul as a vocal pair, fine-tuning harmonies during practice to perfect the stage. When Sagisomul became discouraged after repeated mistakes, Sieun encouraged him, saying, “You can’t lose confidence.” She also comforted and energized the members who were nervous before the main performance. The stage came together under Sieun’s leadership, delivering a moving harmony and vocal blend, and Sieun captivated with her relaxed presence, even performing air-guitar during the set.

Meanwhile, STAYC recently completed their second world tour, STAY TUNED, visiting 8 cities across Asia, 4 in Oceania, and 10 in North America to meet global fans. The group is also preparing for the release of their first full-length Japanese album, STAY ALIVE, on February 11 next year.