Keigo Westwood, nicknamed "Bullet", is a Wyoming police officer involved in the takedown of the Mexican drug cartel La Llorona. True to his name, he charges straight in and rushes through the cartel's defenses, leading to the arrest of all of its leaders. However, at that same time Yellowstone's volcano, which is said to be powerful enough to wipe out all of humanity, explodes. The earth splits, Keigo and the arrestees are swallowed up in it, and when he comes to Keigo is in the 19th century--the era of the Wild West. It is in this world, where all manner of men run free of the law, that Keigo teams up with a vengeful Abraham Lincoln in hunting down the members of La Llorona once again.

After the war, there are many "Extends" in the city, people whose bodies were modified to make them into dangerous weapons. Inui Juuzou is one of them, and he has no memories of his life and body before his head was transformed into a gun. Strangely enough, his head-gun is designed so that only someone behind him can pull the trigger. Juuzou makes a living by taking on cases involving Extends in the city, and he is assisted by Mary, an intelligent young woman that he has taken under his protection.

The sole survivor and witness to the serial kidnapping case that drew national attention 10 years ago was Oyamada Yousuke. In the end, a total of 108 children vanished into thin air and the case remains unsolved. Since that incident, Yousuke has been able to see evil spirits and has been attempting to seclude himself from society. But one day, he meets Kanno, a member of the anti-doll organization. She explains that the spirits that he has been seeing are called dolls and are the manifestation of people’s incredibly strong emotions. Yousuke accidentally releases a doll named Makina that even the organization had to resort to simply imprisoning her instead of destroying her. However, Yousuke learns that Makina has a connection to the kidnapping case that he was involved in years ago!