After a catastrophic accident ends his life, 16-year-old Asaru Takayoshi awakens deep within a nightmarish dungeon, armed with nothing but his instincts and a strange System bent on his survival. But as he gets thrown from one crisis to another and arrives at the end where everything should have been over, he was split. His mind wiped, Asaru wakes up in a hospital in modern Japan, believing he survived a bus accident. Meanwhile, the system created a separate entity from the memory, strength, and identity he once had—a new being named Ace. Emerging and navigating into a world riddled with magic and monsters while branded a mystery, Ace finds himself reborn but detached from his own humanity. As he gets caught in the crossfire of secret factions and fierce battles growing ever stronger, he begins to unravel the disturbing secret truths of his origin, and of this new world. Whatever his pseudo-reincarnation truly was, the world didn't just need a hero anymore.
It needed a code breaker.