In a world where giants that eat humans have spread, humans surrounded their cities with huge and strong walls; to protect what remains of the human race from extinction, thus restricting their freedom to live only within these walls without going outside. However, the unexpected appearance of some enormous giants that surpass the great walls caused a disruption of the security that humans had lived in for decades, leading to our heroes' struggle against the giants to regain their freedom, thereby uncovering many secrets.