Go Ahead, Ghouls, Hit Me / Haunted Into Power: Ghosts Attack, I Level Up!

A broke office worker with maxed-out debt gets jumped by a ghoul. Instead of dying, he awakens a system: every time a ghoul hurts him, he gets stronger. Now his life motto isn't "work harder", it's "hit me harder." His boss gives him a raise. Ghouls give him power. He's starting to enjoy the pain...