Watch Young Sister 3 for Free: How to Stream the Movie Online at 123Movies. . Yeon-jae, who runs a wedding dress shop, decides to use her cousin, Dong-sik, who just got out of prison as her part-time worker, and lets him stay in her house. A sexy employee named Ji-na feels attracted to Dong-sik and flirts with him. Yeon-jae gets back together with Yeon-woo, the photographer, but is shocked to find out that he’s in a deep relationship with Ji-na. Yeon-jae gets drunk alone and crosses the line with her cousin Dong-sik…