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.

An ancient God called Ranga awakens on an isolated island in the South Pacific where it has been slumbering forgotten by mankind. Three sisters living in Tokyo—Minami, Ushio, and Yuuhi Shimabara—discover they have inherited this Island Kingdom, along with the huge God. When Ranga shows up in Tokyo, it soon becomes a source of wonder and conflict for the three sisters that control Ranga, the people who want to destroy it, and ones who want to use it.

According to an ancient legend, mermaid's flesh can grant immortality if eaten. 500 years ago, Yuta unknowingly ate a piece of mermaid's flesh. For centuries, he travels across Japan, hoping to find a mermaid, thinking she may be able to make him a normal human again. When he finally finds one, he discovers that she and her companions have been raising a girl to be their food so they can eat her and take on her youthful looks. That is how mermaids stay young. Yuta kills the mermaids and rescues her, but she has already eaten some of the mermaid's flesh. Although he had to kill the mermaids, Yuta isn't too disappointed. Yuta's once lonely existence is now over, as he has found a companion in Mana. And Mana, who had been trapped in a small hut her whole life, finds delight in even the simplest of things. Together, Yuta and Mana attempt to seek out more mermaids, trying to become normal humans again.

Asa and Kame strike up an immediate friendship when they arrive at the same time for their first day of duty at the Ooku, the splendid pleasure palace housing the harem of Lord Tenshi. The two young women are there to join the many hundreds of other maidservants—men are barred from entering, with immediate beheading the price of trespassing. It soon becomes clear that behind the luxurious lifestyle and ritualized routines of the Ooku lie sinister schemes and cynical rivalries. Meanwhile, a mysterious wandering potion-peddler known only as the Medicine Seller subtly insinuates himself into the Ooku, just as an uncanny, otherworldly menace begins to reveal itself.