The Old Man Vows Revenge Against His Demon Wife

Channel all anger into one fist. A tale of unstoppable revenge action. Seventy years ago, dungeons suddenly opened across the world. Inside them, humanity discovered Mana, a substance that drastically accelerated human evolution. One day, the protagonist Seishiro rescues a woman inside a dungeon. She is an Oni, a high ranking class embedded with superior Mana. Over time, the two build a bond that serves as a bridge between humans and Oni, completely unaware that this very woman would betray him and strip away everything he ever held dear.