In present-day Japan, as the Reiwa era begins, Mizu witnesses a flying shark, but no one believes him until more sharks appear and attack the population. Mizu joins the fight against the sharks, but after losing his loved one and discovering he is invincible, he decides to confront the sharks alone. Along the way, he acquires flames capable of burning everything and mushrooms that allow him to travel to space. But when a colossal golden shark, as powerful as Mizu himself, appears in the sky above Earth, the ultimate question remains: Can Mizu defeat this monstrous foe, or will Japan—and the world—face annihilation?