어느 날, 재벌 오빠가 생겼습니다

Huo Zheng's grandmother lies critically ill, longing for her long-lost granddaughter. Knowing the real one perished, Huo hires Sang Sang—desperate for her father's treatment—to pose as his sister. Her infectious joy revives Grandma's health and sparks Huo's happiness. As deep affection grows between them, both swallow their feelings behind the feigned sibling bond. When Sang Sang's identity surfaces, Huo stands by her, winning the grandmother's blessing to unite.