The narrative unfolds in an era when Earth lies shattered, its hope nearly vanished after a deadly toxin known as 'shinobi' crashed from space on an asteroid. Survivors flee to Kairiku, a former seabed now sanctuary, where they strive to shield themselves from the toxin's ravages. Amid this bleak reality, a solitary beacon of optimism endures: the sacred weapon Giga Road and the famed fighter Yagyuu must unite to neutralize the poison. In the aftermath of a event that left continents scarred and skies dim, the people cling to hope. Their unity is tested as myths awaken, promising salvation through courage and sacrifice. To rescue humanity, Ame, heir of a ruined realm, rises as the world"s savior.