"Never open the box."
Although recognized as a children's toy, the kotoribako is subject to ancient and modern urban legends - quite often involving curses and death.
Read as '子取り箱 ' (small children's box) as compared to '小鳥箱' (small bird box), 'Kotoribako' is a trick box which requires solving a puzzle to open. Kotoribako items are popular among children for their secrecy, however there are multiple urban legends which highlight the ominous and menacing vibes which seem to lie within their depths.
This urban legend was originally one of the variations posted on 2-chan's occult site.
Long, long ago there was a small village which lived tucked away in the mountains of Japan. One day the head of the village discovered a mysterious kotoribako box with a beautiful, intricate design.
Upon parading the box around the village, women and children were drawn to the object - begging the head of the village to open it, however the puzzle was too difficult.
Suddenly, the women and children grew ill - coughing up blood and falling to the dirt as spasm after spasm wracked their bodies. Within days, anyone who had ventured near the box had fallen sick with the mysterious illness, and the women and children who were once so curious to open the box were the first to perish from the violence of the disease.
In hopes of cleansing whatever curse the kotoribako box had brought upon the people, the head of the village locked away the box in the village's shrine - declaring it to never be touched again.
Years later when the horror of the kotoribako box had faded to a disbelieved tale, a group of people found the box within the shrine. After working at the puzzle, the box finally sprang open to reveal the contents.
Inside the kotoribako box were the remains of a human corpse; the head shrunken yet preserved with its eyes wide in a loathsome glare.
Immediately, the people who discovered the box fell to their knees while gagging on mouthfuls of blood as they choked and spasmed.
Within hours, the population of the village was decimated as men, women, and children fell to a quick and violent death; their screams ringing out over the mountains.
No one survived.
It is said the cursed kotoribako box still exists in rural Japan, but the village's location and shrine's name have been forgotten.