The Yang world is where the living live, and the underworld is where the dead souls return. There are countless "yin gaps" between the two worlds - most of them are concentrated in old alleys, abandoned hospitals, mass graves, ancient houses and other places with strong Yin energy. They are passages for dead souls to stay in the Yang world and for evil ghosts to break through the world.
The balance of yin and yang is the law of heaven, and the core responsibility of the night watchman is to seal the gaps in the yin, transfer good souls, kill evil ghosts, and protect the boundary between the two realms from being breached.
