In a world where the title of Hero is treated as a punishment rather than an honor, the worst criminals are sentenced to the front lines of an endless war against the Demon Lords. Branded as Heroes, they are forced into military service without even the mercy of death, condemned to be revived and sent back into battle forever.

Among them is Xylo Forbartz, once a respected commander of the Holy Knights. Now the leader of Penal Hero Unit 9004, he commands a squad of convicts considered expendable by the very nation they serve. During one chaotic mission, he encounters Teoritta, a living weapon known as a Goddess, whose presence threatens to shift the balance of both the war and his own fate.

As the unit is sent on increasingly dangerous operations, Xylo must balance leading his unit, surviving the battles he finds himself in, and uncovering the truth behind his own sentencing.