A naïve youth named Ikuroo bears a parasite called Baoh, which was surgically inserted into his skull by the sinister syndicate Doress. The organism grants him near‑immortality and lets him morph into a formidable beast whenever danger looms. Doress plans to exploit Ikuroo for monetary gain, global control, or a similar scheme. However, during a train transfer, Sumire—a telekinetic girl held captive by the same group for her powers—breaks him loose, and they flee together. Their escape draws the attention of Doress"s elite security, who launch relentless pursuit across the countryside. They navigate through crowded stations and hidden tunnels, hoping to stay ahead of the relentless pursuit. Dr. Kasuminome, the deranged scientist who engineered Baoh, will not allow his experiment to escape. He wields an army of empowered henchmen and other formidable forces to hunt them down.