Narrator Kō Ibaraba, 27, lives in Morioka, a prefectural capital in northeastern Honshū. Upon completing her degree at an art college, she took a job teaching art in middle school, but after two years decided it wasn’t for her and quit. Now unemployed, and being of a reclusive nature to begin with, she spends much of her time closeted with her beloved manga. That summer, her centenarian grandfather Rei Ibaraba dies. He had been a prolific but never tremendously successful author of mass-market genre fiction, mainly in the horror vein. He doted on Kō when she was little, and she had grown up reading the books in his library. As she is going through his effects, she finds a note he left for her between the pages of Sanaki no mori (The Dismembered Ghost), a work from relatively early in his long career. He asks her in the note to go to a shrine in Sayo village, near Tōno in the mountains to the southeast, to retrieve a decorative obi clasp hidden there, and to place it on his grave. The story proceeds by moving back and forth between what Kō learns about her grandfather’s past on her trip to Sayo, and the narrative of the book in which he left his note. Its story line appears to be closely based on tragic events that he and a friend named Ono had played a part in some eight decades before.
The main plot of Rei’s book revolves around the unusual custom of posthumous marriage in Sayo: when a man meets a premature death without ever knowing matrimonial bliss, the village takes pity on him and finds him a bride. The woman who marries the deceased then spends her days reading Buddhist sutras, and is forbidden to leave the house or its grounds except when there is a death in the family. In accordance with this practice, the Tōjōs, the most prominent family in the village, find a bride for their second son, who has died while away in Manchuria. She is an orphaned beggar woman named Tatsuko. When Reido Ariba (= Rei) and a friend named Shōno (= Ono) visit Sayo for a month to take the water cure at the hot springs there, a complex triangular relationship develops between the two of them and Tatsuko, the upshot of which is that Shōno commits suicide upon returning home. Shortly afterwards, Tatsuko’s mother-in-law is killed in a gruesome manner while locked in a storage shed.
In the framing story, narrator Kō and 14-year-old Ruiko Tōjo, Tatsuko's great-granddaughter, who befriends Kō when she arrives in Sayo, go about solving this classic locked-room mystery that had remained unsolved at the time?with a little help from Kō’s former art teacher, Jinno, who’s exact relationship to Kō is also tantalizingly mysterious until the end. The reader eventually learns that Tatsuko was responsible for the murder, but she covered up her crime to the other villagers by making it look like the work of a dismembered female ghost of local legend known as Sanaki. She also seduced her brother-in-law and effectively took control of the Tōjō house. Having himself solved the mystery, Rei had in fact hidden a damning piece of evidence in order to atone for his role in Ono’s suicide. He had then written Sanaki no mori in part to let Tatsuko know what he had done?by placing a message in it that only she would recognize.
With consummate skill belying the fact that this is her debut novel, author Azami Saidō masterfully interweaves the framing and embedded stories while maintaining two distinct styles for them?adopting the flavor of a contemporary light novel for the former, while casting the latter as a dark and grotesque tale of horror from long ago, rendered in the linguistic style and orthography of the early 20th century.