‘A Yao Sends a Letter’ #TheLongestPromiseOST# A thought becomes a calamity, love travels far; a dream of empty mulberry, hard to escape fated bonds. #TheLongestPromise# The original soundtrack is now online, featuring @胡夏 @TIA袁娅维 @刘惜君 @双笙子 @谭杰希JakiTam @狗子你变了en singing the love song of the empty mulberry together, along with 31 theme tracks, composing a lifelong passion in the dream of jade bones.