Chen Mo, a programmer who was extremely involved, died unexpectedly and came to the underworld. Unexpectedly, he turned out to be a troublesome "overflow bug" in the Underworld Group's thousand-year system - the soul number exceeded the limit, and an error was reported! In order to "register" for himself and pave the way for those who come after him, Chen Mo must find a solution in this eternally rotating "code mountain". He met his predecessors who had become immortals after catching fish, colleagues who were stuck in endless overtime, and he also faced the sadness of memories fading with the passing of human thoughts. Under the "iron rice bowl" of "never losing his job" in the underworld, Chen Mo began to think: How to find the real sense of life and create his own value in the almost infinite time? This is a wonderful journey about saying goodbye, adapting and finding meaning in difficult situations.