Where's the Promised Immortality? You Want Me to Kill the Immortal?

I thought it was a cliché story about a boy from an ordinary mountain village who accidentally finds immortality, but I didn't expect that the introductory manual for cultivating immortals I picked up said: "Lesson 1: Kill the Immortal." The manual told me that the immortal world has long since decayed, and the immortals use the suffering of the human world as a resource for spiritual practice. I hold this iron ruler that can hurt immortals in my hand, and look at the immortal patrol official hanging in the sky. He is smiling and extracting the longevity of the whole village. The immortal official said: "Kneel down and grant you immortality." I laughed. ---