In a world with an alternate history, a great war finally comes to an end leaving the earth diseased and polluted. The geneticist Dr. Azuma vies for support from the government for his neo-cell treatment that he claims can rejuvenate the body and regenerate humankind. The government leaders, guarding their own deeply entrenched powers, turn down the professor. Driven to complete his work, Dr. Azuma accepts a secret offer from a sinister faction of the powerful military. After an incident occurs in Dr. Azuma's lab, a race of mutant humans known as the Shinzo Ningen are unleashed upon the world. Now only the warrior known as Casshern, reincarnated with an invincible body, stands between the Shinzo Ningen and a world on the brink of annihilation.

The prequel to the horror film Ringu, this movie provides the background story of how Sadako later became the vengeful murdering spirit. The story starts with her as a shy, somewhat withdrawn, college student who nonetheless gets involved in a drama club. The director thinks she has talent, but some of the other performers start to get jealous of the attention he gives her. Meanwhile, a reporter investigating Sadako's spiritualist mother thinks there's something very suspicious about the young woman, and arrives on campus to confront Sadako just as a series of strange deaths start sweeping through the drama club.

Japan, 250 years ago. Soetsu is a moneylender who is killed by the cruel samurai Shinzaemon. His body is dumped in the Kasenega-Fuchi river. According to legend, all who drown in the river will never surface again. 20 Years later, Shinkichi, the handsome son of Shinzaemon, coincidentally meets Toyoshiga, the daughter of Soetsu. They fall in love. It is a doomed love, as the spirit of Soetsu is far from dead.