Kazuki Azuma returns to Japan after ten years away, only to be chased down by the Bubuki police. He's saved by a childhood friend, Asabuki Kogane, and her right-hand-shaped Bubuki. He then meets the Bubuki users Nono Hiiragi, Ougi Kinoa, and Taneomi Shizuru. Azuma has never even heard of Bubuki, but after learning that he's the user of the "heart" Bubuki, he makes his way to the Buranki prison in Shinjuku's underground to awaken the sleeping Buranki called Oubu.

As Oubu finally achieves its complete form, Entei stands before it controlled not by Reoko, but by Zetsubi. Laughing boldly, she tells the shocked Azuma that he can't beat Entei, but Kinoa insists that they and Oubu are different from before. Zetsubi is cornered by Oubu's ferocious attack, so she takes the Russian team's Bubuki to use as Entei's limbs, and Oubu is overwhelmed again. Can Azuma and his party win this fight?

The foreign teams continue to hunt the headless déraciné Buranki, so they can take its heart and use it to awaken Buranki in their home countries. Meanwhile, Arabashiri is fighting his own battle for Reoko's sake. He has watched Reoko endure the ceaseless pain of fighting déraciné Buranki one after another with the incomplete Entei, and now his rage explodes on Azuma's mother, Migiwa.

As Reoko, full of bitter resentment, grasps Migiwa in Entei's hand to try to crush her, both women look back to when they were sixteen years old and best friends. Reoko called forth Entei in Ueno to bring the long-buried existence of Buranki to light, but Migiwa burned Entei's limbs to stop this uprising, which left Reoko's body with the curse it still bears today. Why did Reoko decide to walk a path of blood after she was released from her years of confinement? Their hidden past is finally revealed.