In a world invaded by monsters from another realm, warriors known as Busters are humanity’s only defense. Toru Saejima, a high school boy branded as talentless and unfit to become a Buster, loses everything when a monster suddenly kills his beloved mother. Powerless and desperate, he flees—only to encounter a mysterious and beautiful woman in danger. Saving her seems like a miracle… until Toru realizes she’s actually a monster, one of the very beings he’s meant to hate. Yet, unable to abandon her, Toru takes her in, and the two begin living together. With revenge burning in his heart and a new bond to protect, Toru awakens a hidden potential. Step by step, the weakest dropout begins his path as a true Buster—one who levels up by gaining the affection of the very monsters he once despised. A tale of vengeance, unlikely companionship, and a rise from weakness to strength begins now.