Shen Yao was originally a female ghost. Because she killed too many people in her previous life, she went to the Abi Hell after her death. A hundred years later, she was unable to re-enter the reincarnation because of her deep obsession.
Due to some chance, he got some free time in the underworld and avoided the fate of turning into a wandering soul.
Because he is only a nominal agent and not an orthodox ghost agent, he can only do some underground business...