Gou Works as an Undercover Agent in the Demon Sect, but His Boss Is a Witch?

After traveling through time and space for many years, Lin Fan finally opened a restaurant in a small town and was about to make a living, but he was targeted by a "fairy" - she was shocked by his (thought to be) useless "outer world" temperament, and insisted on sending him to undercover the notorious "Netherworld Demon Sect", promising to help him become a pillar of the righteous path after the incident. With "the heart of righteousness" in his heart, Lin Fan cautiously sneaked into the Demon's Cave, only to find that something was wrong with the sect: his senior sister was too enthusiastic, and the elders always praised him for his "deep immortality." Wait! Is it the Demon Sect or the Immortal Sect that I am undercover? Where is the promised light of righteousness? So I am the undercover demon? !