In a clash between the Dragons of Heaven and the Dragons of Earth, Princess Hinoto foresees humanity's impending doom. Kamui Shirou, a pivotal figure at 15, stands at a crossroads: side with the Dragons of Earth to safeguard the planet by eradicating civilization or join forces with the Dragons of Heaven to preserve mankind. Honoring his late mother's request, Kamui returns to Tokyo after a six-year absence, aiming to seize the Sacred Sword safeguarded by Kyougo Monou, father to his childhood companions Fuuma and Kotori. Despite his failed attempt, a mysterious figure seizes the sword instead. Convinced that Kamui fulfills her prophecy, Hinoto dispatches the Dragons of Heaven to recruit him. Initially resistant, Kamui grapples with his role, but relentless assaults by the Dragons of Earth on his loved ones force him to weigh the value of his friends' lives against the fate of the world, compelling him to make a fateful choice.