A mysterious phenomenon occurs in a hot spring in Beppu. It foreshadows the appearance of the legendary giant monster Bugon, a guardian deity who has been watching over Oita since ancient times. The locals band together to stop the rampaging Bugon, who releases hot spring water from his mouth, but...

An attack takes place on Rainbow Bridge in Odaiba, Tokyo by the fighter helicopter `Gray Ghost`. 2 days earlier, the Gray Ghost was stolen. The perpetrators are followers of Yukihito Tsuge. Yukihito Tsuge planned a coup of Tokyo 13 years earlier. The leader of Special Vehicle Section 2, Keiji Gotoda, sets out to stop the terrorists.

A mysterious space sage entrusts Yuma with challenges that surpass the limits of his imagination with a stake too high. He asks, "Should you fail… then you… will lose your power as Arc." The burden of protecting Hoshimoto City alongside SKIP members are twisted by Sascal, who manipulates them, sending challenge after challenge toward Yuma. Battling giant kaiju, an evil alien bent on destruction, and a warped dimension where even time itself is distorted, Yuma must confront the ultimate test. Will he... will Ultraman Arc overcome the greatest challenge yet and protect the future, surpassing the limits of the power of imagination?

The story begins with an indiscriminate slaughter at a cafe frequented by young people. Security camera footage shows an unarmed man with shaven head, able to seemingly kill people with a simple touch. Police investigation leads to the suspected identity of the murderer: middle-aged man named Tarō Yamada. When the police conduct a search of his apartment, they find the rotting corpse of a woman. Adapted from Sato Jiro's own debut manga.