Japanese Urban Legends

Gozu

Gozu, translated into Cow Head or even Ox Head, is a Japanese urban legend about a story that is so horrifying that people who read it or hear it are so overcome with fear that they tremble violently for days until they eventually die.

One variation of the story involves a teacher who tells a fragment of the story to his class while on a field trip of some sort, which results in the children becoming paralyzed by fear and even losing their memory after their school bus crashed. Other variations of the story includes the detail that no one is able to re-tell the story, since they die after hearing it. 

Rumors say that only bits and pieces of the actual story remains, including one that talks about a town that got cursed after they ate the Cow Head. 

The legend was rumored to be an unpublished piece of science-fiction written by author Sakyo Komatsu, however there is no evidence to prove this rumor. 

Though, other stories and legends with similar titles do exist. A Ukrainian folktale called "Cow's Head" is said to be about a woman who receives good fortune by offering food and shelter to a disembodied cow's head that visits her one night. However, this folktale isn't horrifying compared to how the Japanese Urban Legend is said to be. Therefore, I don't believe these stories are in anyway related other than their shared title.