Jiangcheng Middle School's library has a message corner on the fifth floor, the top floor. Beside the window stands a wall of lockers, 1.8 meters tall and 2 meters wide, containing 144 locked compartments. Each compartment holds a notebook. Any student or teacher at Jiangcheng Middle School can apply to use one through the library office. Keys are issued at the beginning of each month and returned at the end. One compartment is different: number 139. Each compartment has two keys, one as a spare, but compartment 139 has only one key, and it cannot even open the lock. Cheng Xin found the key to compartment 139 among the flowers outside the library. To her surprise, it opened the compartment, where she discovered a notebook... It had been written by Xiang Nan, who had been unconscious for nearly two years. The notebook chronicled everything that had happened during that time, and its recent entries mentioned Cheng Xin. Curious, she assumed it was a prank, only to discover that the notebook really had been written by the Xiang Nan she knew... By chance, Cheng Xin encountered Xiang Nan in spirit form. Together, they began investigating the mystery of the spirit diary. Who is the diary's true owner? What secrets does it hold? How did Xiang Nan fall into a coma? Can Cheng Xin help him return to his body? Can those lost and confused in their youth find their way in life? It seems all the answers are waiting to be found...
