In ancient China, a young musician named Yu Boya gained fame for his talents. On the night of the Moon Festival, he encounters a mysterious woodcutter who is also a musician and admires Boya's most famous song: Lofty Mountains and Flowing Water. Their friendship deepens and Boya vows to play the song for his new friend every year on the festival night. But the next year, upon hearing of his friend's death, Boya smashes his instrument and never plays again. To this day, the word for "close friendship" means "understanding the music."