[Quick Transmigration] The Immortality Code

Li Haoyu, who died young, received a mission from an envoy of the Underworld: Find the Underworld's missing Crystal of Immortality. To help him, the Underworld assigned him a partner codenamed Eighteen. And so, two cannon fodder characters set out on a grand quest no one had ever completed. Waiting for them were the ultimate challenges posed by four races: vampires, merfolk, werewolves, and the undead. Eighteen: Our destiny is to complete this epic mission! Li Haoyu: Damn it, I just want to follow the plot in peace and, while I'm at it, stay alive! Eighteen: Aren't you already dead? Li Haoyu: ... Reading notes: 1. This is a quick-transmigration story that could be called