In the Apocalypse: From the Start, I Was Tricked into Slaying a Dragon

“In three years, a dragon will destroy the world, shattering a planet with a single breath! If you don't want to die, hurry up and level up!” Su Han believed the System. He spent three years desperately keeping his head down and honing his dragon-slaying skills, waiting for the day he could face the dragon in a fight to the death. The apocalypse arrived right on schedule. He opened the door... There was no colossal dragon blotting out the sky, only a bunch of sluggish little zombies groaning and shuffling around. Su Han stared at the dragon-slaying blade in his hands, powerful enough to cleave stars, and was completely dumbfounded. “Damn System! What happened to slaying a dragon?”