The Door.

Zung comes to Korea to investigate the mysterious death of her father, Seijung, a renowned performer and composer in the Japanese music scene. While Zung pursued a different path in life by studying engineering, she is drawn back to her father's legacy. In her search, she reaches the summit of Hallasan, where her father's body was found, and meets Master Woo, a master of the gayageum, and his daughter, Gasil. Listening to Master Woo's performance, characterized by the phrase "music that is joyful yet not exuberant, sorrowful yet not mournful," she learns that her father had been deeply affected by the music, leading to his tragic passing.