In a world overrun by mysterious monsters, humanity creates enhanced warriors known as Heroes to fight back. At the Hero Academy, sisters Sakuya and Kaguya train together to protect humanity. However, they are captured by the Demon King Mara, who begins a twisted plan to corrupt and reforge them into his loyal followers. As their wills are tested, the truth behind Mara’s motives begins to unfold— a dark fantasy story about control, transformation, and the meaning of true strength.