Hyun-woo, a former billionaire heir, now lives a quiet life juggling three jobs. When Seo-yeon, who he had a one-night encounter with, reappears with their daughter and demands marriage, they suddenly become a family. As a crisis threatens her company and family, Hyun-woo steps in to protect them, while Seo-yeon still believes he's a poor man. Will she discover his true identity?