I Died 999999 Times – Infinite Level Up with Invulnerability Skills回死んだ俺　～不死身スキルで無限レベルアップ～

The strongest hunter guild, “Byakuren”, is praised as the world’s heroes after defeating the Demon King. However, the truth hidden behind their power is utterly inhumane. Their strength comes from a cruel secret—they imprison two siblings, Makoto and Minori, who are descendants of the undead, repeatedly killing them to forcibly farm experience points. To survive—and to take revenge—the siblings make a mad choice: killing each other to level up. “Let’s begin—our revenge.” Awakened through their deadly struggle, the two carve a path of vengeance.