[Ghost Hunting, Sweet Romance, Wish Fulfillment, Metaphysics, Magical Duels]
People who deliver letters in the world of the living are called postmen. Those who deliver letters between the worlds of the living and the dead are called Yin-Yang Couriers. They usually keep a low profile and never meet their customers. Every letter is delivered on the strength of their word.
After Zhang Lin joins a mysterious organization, he becomes a Yin-Yang Courier. During a chance encounter, he rescues Su Yao, whose good fortune has run out, and gives him a chance to be reborn. After that, however, paranormal events keep happening around him...
When Zhang Lin asks why the organization recruited him, its leader simply says that fate brought them together.
But when Zhang Lin delivers a letter to the underworld, he discovers that even its high-ranking officials treat him with great respect.
Later, he joins a special department. While organizing its files, he finds records of an upheaval fifty years ago. But when he asks the old-timers about it, they are tight-lipped.
Then he hears from a woman who claims to have been his junior sister in a past life that he was once a powerful cultivator. During that upheaval, he single-handedly put an end to it, but died after burning through all his strength.
A conspiracy slowly closes in around him...
