The Enigma of Amigara Fault is a short story included at the end of Gyo.
Following an earthquake in an unnamed prefecture, a fault is discovered on Amigara Mountain (the name Amigara meaning "empty shell"), very close to the epicenter of the quake.
A hiker named Owaki is climbing the mountain when he meets another hiker called Yoshida. He assumes that she is there to see the fault, which has captured the attention of the global press. The pair follows the sound of voices to the site, and marvel at the strange site: countless human-shaped holes in a rock face exposed by the earthquake.
Scientists examining the holes announce that there is no way to find out how deep into the mountain the holes go. The holes are not natural and must have been dug from the inside. They figure that the accumulation of soil over the centuries eventually sealed up the entrance, yet they have no way of knowing why the holes were made or who would have the technology to do it, especially since they appear to be thousands of years old.
Owaki is distracted from the speculation when he notices Yoshida looking for something. She explains that she came because she saw something on TV: a hole that she swears was her exact silhouette. Ever since she laid eyes on the hole, she has had a strange feeling that it was meant for her to enter. Owaki is skeptical, but another man called Nakagaki overhears and says that the same thing happened to him. Most of the people who have come to the mountain are looking for their own holes. Nakagaki reveals that he has finally found his own hole, and disappears into it before Owaki can stop him.
The scientists' equipment can find no trace of Nakagaki. A rescue squad is dispatched, but it has to retreat after getting no more than five meters inside the hole. While camping at the fault overnight, Owaki has a nightmare in which he is Nakagaki, trapped deep inside the mountain and unable to move because the hole has been deformed by the earthquake. When Owaki awakes, Nakagaki still hasn't been found, but Yoshida tells him that she has found her own hole at the foot of the mountain. Despite Owaki's continued skepticism, she insists that it was made for her thousands of years ago, and when she goes inside, she will be trapped just like Nakagaki.
Suddenly, a commotion erupts In front of a news crew reporting on Nakagaki's disappearance: a young man has scaled the wall to one of the holes. He shouts "This is my hole! It was made for me!" and disappears inside. Some other people present at the site then begin climbing into "their" holes as Yoshida says that hers is calling to her and beckoning her inside. Growing increasingly hysterical, she admits that she is afraid that she'll die in there, but feels she has no choice but to go. Owaki blocks up the hole with rocks in an effort to reassure her. That night, they share a tent because Yoshida is too scared to sleep on her own. Owaki comforts her and she tells him how lonely she is. He says that her loneliness made her become attached to the idea of the hole, but now he'll protect her. They kiss.
That night, Owaki has another dream; he is a criminal in the ancient past who has committed a horrific crime. His sentence is to enter a hole in the mountain that was dug out specifically for him, carved in such a way that made it impossible to move anywhere but forward. As he walked through it, his limbs and neck were torturously stretched and distorted, far beyond any normal humans; somehow, he remained alive and in agony. Owaki wakes to find that Yoshida has unblocked her hole and disappeared into it. As he sits mournfully by the mountain, to his horror his dropped flashlight reveals his own hole nearby Yoshida's. He is compelled to take his clothes off and go inside.
Several months later, the scientists are informed of another fault on the other side of the mountain. There are more holes, but they're not human shaped - they are elongated and curved randomly, having no true shape. One worker decides to examine one of the holes and shines his flashlight inside. The scientists see something hideous slowly sliding towards them. It is the body of one of the people who had entered their hole on the other side, horrifically disfigured by the warped tunnel - but still, somehow, alive and coming ever closer...
This story's horror factor is based on the psychological aspect of compulsion. As the holes are "made for them", they feel the irresistible need to enter, despite knowing the result being death. Famous psychologist Sigmund Freud describes this feeling as "death drive", unconscious instincts that seeks to destroy the individual. As in the case of having the thought of jumping off a cliff when near one, for example; this feeling is also known as "call of the void".
The psychological aspect of this story thus drives its horror. Essentially, it is the story's characters killing themselves - something inherent within them causes a deep urge to destroy their own self. As there are no evil forces/enemies presented in this story, it emphasizes the internal psychological factor - that is, it is possible for people to actually have a desire to harm themselves (such in the case of mentally disturbed persons, and those unable to control their instincts and unconscious, similar to all those that enter the holes in the story). As such, the story comes to explores the innate human instincts of curiosity and destruction (which is also present in Ito's other works) which can, invariably, be the end of themselves.