Only Shuishu masters such as Yang can read and decode old scripts copied by hand from generation to generation, combined with the oral accounts taught by their teachers. The precious books record encyclopedic knowledge about the ancient Sui ethnic group, ranging from astronomy, geography, religion to philosophy.

"Shuishu contains the Sui people's origin story, migration history and understanding of almost everything. I've been trying my best to preserve our precious culture," says Yang, from Sandu Sui autonomous county in Qiannan Bouyei and Miao autonomous prefecture, Guizhou province.

In November, the Shuishu character documents from Guizhou were added to the UNESCO Memory of the World Asia and the Pacific Regional Register. Yang did much work for the application process.

He's the fourth-generation Shuishu master in his family. Imperceptibly influenced by what he saw and heard in the family, he became interested in the ancient characters and made up his mind secretly as a child, yearning to be a master successor. His uncle told him that only a kindhearted person would be chosen as the Shuishu inheritor of the family.