Each night, young Toramizu Ginta dreams of a mystical realm, yearning to explore its wonders. Amidst skepticism from most but unwavering support from his friend Koyuki, Ginta remains hopeful. Suddenly, a massive door materializes before him, beckoning him into the enchanting world of MAR Heaven where powerful ARMS reign. Thrilled by this new reality at first, Ginta's excitement dims as he uncovers the dark history of war that once consumed MAR Heaven and the ominous threat looming on the horizon.