Complex sentence: To his surprise, Young-sae learns Chae-ryn knows nothing about dancing and her soon-to-be married, older sister, Jang Chae-min, is the talented dancer.
Split into simpler sentences: To his surprise, Young-sae learns Chae-ryn knows nothing about dancing and her soon-to-be married. Older sister, Jang Chae-min, is the talented dancer.