The Penalty Skill That Reduces My EXP If I Don't Act Like a Hero Makes Me Overpowered

The Hero before me failed. Not because the Demon King defeated him. Not because he was too weak. But because he stopped acting like a Hero. In this world, Heroes possess a unique skill: Hero Qualification. Act selfishly, cowardly, or foolishly, and you lose experience. The previous Hero lost everything. Then died. Now it's my turn. My name is Kazami Genma. A shut-in. An anime addict. A man with absolutely no intention of behaving like a proper Hero. The Angel who summoned me thinks that makes me the perfect weapon against the Demon King. The Devil running the other side of this ridiculous game seems to agree. Unfortunately for everyone involved, neither of them bothered checking how the experience system actually works. And somewhere in the Demon Realm, the Demon King Airi is already reading the rules more carefully than either of them. A comedy about a Hero, a Demon King, an Angel, a Devil, and a game system that was never properly tested.