A page from the ninja technique textbook discovered in the Hirosaki City Public Library is seen in Hirosaki, Aomori Prefecture. (Photo courtesy of Shigeto Kiyokawa)

HIROSAKI, Aomori -- An original copy of a ninja technique textbook believed to date back to the 18th century has been discovered at a public library here, the adviser of the Aomori University ninja club has disclosed.

This is the first time that such a textbook has been found in Aomori Prefecture, said club adviser Shigeto Kiyokawa, 57, a professor in the faculty of pharmacy at Aomori University. He has also confirmed that an old private house in the city was used by ninja in the past.

The 12-page textbook discovered at the Hirosaki City Public Library contains explanations about how to make weapons and use charms. Also among the skills detailed in the text is a method for combining gunpowder and aconite to make a dust to blind enemies and a mysterious technique for making a sleeping medicine by burning dried toads and mandarin ducks. The textbook also instructs ninja to secure a single doorway for use when staying at an accommodation facility and to prop up a tatami mat against the door to alert them to intruders.

The old book was discovered in March by Tetsuya Ueda, a ninja researcher in Kyoto, when he visited Hirosaki for his work.

Based on similarities in textbooks discovered in other regions and other factors, "There is a high possibility that it was written to hand down ninja techniques to the next generation in around 1756 by the ninja group Hayamichinomono," Kiyokawa said.

The group served the Hirosaki feudal clan, and was a branch of the Koka school in Shiga Prefecture in central Japan. Hayamichinomono temporarily dissolved around the time that Kiyokawa believes that the book was written.

"It is now clear that Hayamichinomono actually used ninja techniques and small tools," said Kiyokawa. "I hope that this discovery will prompt other people who have similar material to come forward."

(Japanese original by Shunsuke Ichimiya, Aomori Bureau)