Immortality is something many people would wish for. But would it be such a coveted ability if people knew they would be subject to countless attacks because of it? Such is the case for Rin Asougi, an immortal private investigator, because there is no shortage of people who want her dead. Over the centuries, she has met many grisly ends, but each time, she returns to life as if nothing had happened. In 1990, while looking for a lost cat, Rin runs into Kouki Maeno, a man who feels that his memories are wrong. Agreeing to help him, Rin discovers that Kouki is not what he seems, all the while drawing closer to her true enemy. This adversary knows Rin and her kind all too well, and if she dies by his hand, she may stay dead permanently.

In the town of Kurouzu-cho, Kirie Goshima lives a fairly normal life with her family. As she walks to the train station one day to meet her boyfriend, Shuuichi Saito, she sees his father staring at a snail shell in an alley. Thinking nothing of it, she mentions the incident to Shuuichi, who says that his father has been acting weird lately. Shuuichi reveals his rising desire to leave the town with Kirie, saying that the town is infected with spirals. But his father's obsession with the shape soon proves deadly, beginning a chain of horrific and unexplainable events that causes the residents of Kurouzu-cho to spiral into madness.

Spirits have always been attracted to Keitarou Gentouga due to his strong spiritual presence. A traumatic encounter with one had caused his right hand to be cursed, forcing him to wear a glove at all times. Now a college freshman, Keitarou is trying to live as normal a life as possible. With the encouragement of his childhood friend Eiko Houzuki, he becomes a private tutor. Since he is at the top of his intake class, his first client is the tutoring firm's most promising student, Yayoi Houzuki. To Keitarou's surprise, Yayoi is Eiko's cousin, and she possesses two pupils in each eye—allowing her to see into the spirit world and purposely seek vengeful spirits to exorcise. Ever since a car accident killed both her parents, Yayoi has been searching for the powerful spirit that kidnapped her mother's departed soul. Seeing that spirits are so attracted to Keitarou, she ropes him into helping her collect other evil spirits that will assist in her future fight. Although her quest is dangerous, Keitarou reluctantly decides to join her, even as each new spirit they meet has him questioning his resolve at every turn.

In the year 19XX, after being betrayed and left for dead, bravehearted warrior Kenshirou wanders a post-apocalyptic wasteland on a quest to track down his rival, Shin, who has kidnapped his beloved fiancée Yuria. During his journey, Kenshirou makes use of his deadly fighting form, Hokuto Shinken, to defend the helpless from bloodthirsty ravagers. It isn't long before his exploits begin to attract the attention of greater enemies, like warlords and rival martial artists, and Kenshirou finds himself involved with more than he originally bargained for. Faced with ever-increasing odds, the successor of Hokuto Shinken is forced to put his skills to the test in an effort to take back what he cares for most. And as these new challenges present themselves and the battle against injustice intensifies, namely his conflict with Shin and the rest of the Nanto Seiken school of martial arts, Kenshirou is gradually transformed into the savior of an irradiated and violent world.