My Hero System Is a Demon Lord's Undercover Agent

The instant Zhang Yi is bound to the “Hero System” upon transmigrating, he thinks he’s the chosen one, until the System posts its first quest: “Bring His Majesty the Demon King a bubble tea with 30% sugar and less ice. Miss the deadline and lose 50% of your life points.”

Holding the drink outside the Demon King’s castle, he discovers that the System isn’t just a fake: it’s a “life assistant tool” from the Demon King’s faction. The quests that follow are even more ridiculous: comb the Lich’s pet skeleton’s “hair,” tell a man-eating flower cold jokes to make it bloom, and mend the Fallen Angel’s feathers after they’re blown off by the wind...

To stay alive, Zhang Yi has no choice but to keep the title of “Hero” while serving as the Demon King’s butler. Then one day, while using dish soap to clean the Lich’s laboratory beakers, he accidentally discovers that “surfactants can improve the stability of magic potions.” While teaching the skeleton to use a pulley system to move piles of bones, he figures out that “mechanical structures can optimize the flow of magic arrays.”

From then on, everything takes a sudden turn:

The Demon King chases after him to ask, “How do I turn a microwave into an instant fireball oven?” The temple knights secretly buy his book, A Guide to Knocking Dragons Flat with the Principle of Levers. Even the slimes by the roadside hold up leaves and beg, “Boss, teach us how to use osmosis to store enough energy to evolve!”

The whole world is scrambling to get hold of this “walking treasury of modern knowledge,” but Zhang Yi just wants to grab the System and yell: Wasn’t I supposed to be a hero saving the world? How did I end up as the comic-relief technical consultant to both the gods and demons?!