The second chapter in volume 14 of the Horror World of Junji Ito series, The Story of the Mysterious Tunnel .
Thirty years ago, Gorou's mother committed suicide by jumping in front of a train as it came out of the tunnel. She was one of many suicides there, and soon afterwards the tunnel was taken out of use.
Some time later, Gorou goes with his friends to explore the tunnel. They talk about local rumors: the surrounding is known as "Demon Hill", it is believed to contain an unknown supernatural force that summons people there, and after the tunnel was built, accidents and suicides began to happen. At one point a major train crash took place and although there were survivors, most of them went missing while trying to escape the tunnel, as did the rescue crew sent to the scene. It is reported that ghosts appear in the tunnel.
Gorou's sister Mari shows up, not knowing how she got there. Their father is convinced his wife was lured to the tunnel by whatever lives there, and that now it's after Mari. The following day, Mari disappears again, and her father goes to look for her. When the two don't return, Gorou traces their footsteps to the tunnel. He walks far enough that he comes across a research laboratory in the middle of the tunnel. Mari is waiting with the scientists who found her, but no one has seen their father. They also see that blood has dripped onto Gorou's head from the ceiling.
One of the scientists agrees to take Gorou and Mari out in a car to search for their father at the back end of the tunnel. However, they don't find him. The scientist says that the research laboratory studies cosmic rays, and they have only recently begun using the tunnel, but there have always been mysterious problems or strange results from their experiments.
Gorou and Mari's father is never found. Mari regularly returns to the tunnel without meaning to, and the scientists have to call Gorou to get her. They suggest he and Mari move in with family a long way away, so she can't come to the tunnel. Meanwhile the scientists note that all of them feel strange, sleepy, and "heavy" when they work in the tunnel. A photograph they developed shows what looks like human faces flying all around them. They believe these entities are passing through the scientists' bodies and causing them to feel ill. The scientists decide it's too dangerous to continue working there, and the laboratory is shut down.
Gorou and Mari prepare to move in with an aunt, but on the day they're supposed to leave, Mari disappears. Just as Gorou is going to look for her in the tunnel he receives a call from a terrified Ms. Koyama, one of the scientists. He goes into the tunnel to find that the other two working on the team are being mysteriously sucked into the walls and ground, while Ms. Koyama and Mari watch in horror. Mari is soon sucked in as well. Gorou and Ms. Koyama run, but Ms. Koyama soon falls victim to the tunnel, having told him that she and the others were mysteriously drawn to return there after the laboratory closed down. Gorou is pursued by the ghosts of the tunnel's former victims as he escapes.
Gorou moves in with his aunt and grows to be an adult. He begins to feel weak and sleepy like the scientists, and never recovers despite going to doctors. Many years later, his aunt tells him about more "accidents" and "suicides" happening at the tunnel and believes it is cursed. She dies shortly afterwards and Gorou feels compelled to return to his hometown. It is now completely deserted, but he knows the tunnel would never really let him leave, and considers that it has been waiting for him. As he steps inside he sees many familiar ghosts including his father, Mari, and the scientists.