Ninja’s secret notebooks and techniques passed down at descendant home

Textbooks detailing covert techniques used by ninja – Japan’s feudal mercenaries – and written pledges on their secret missions were passed down for generations at the home of a ninja descendant in western Japan, according to analysis of ancient documents found there.

Experts in Japanese history say the documents discovered in 2000 in Koka, Shiga Prefecture, are valuable because they prove ninjutsu techniques employed by ninja involved in such missions as espionage, sabotage and assassination were handed down to the next generations in the western Japan city.

Koka and Iga in Mie Prefecture, central Japan, are widely known as the home of the two most famous ninja clans. Ninja gradually diminished in Japan’s Edo period, from 1603 to 1868.

Among around 150 items found in the house of 79-year-old Toshinobu Watanabe, 17 were textbooks on such subjects as how to make poison or conduct night attacks. Of the 17, four were written in the 1670s and 1680s, according to research by the Koka city government since last year.

For example, one of the textbooks on poison instructed ninja to put into wells powder made by burning lizards or tiger beetles that were believed to be poisonous.

Another one on sleeping medicines said enemies would fall asleep when smoke is emitted by burning powder made from insect shells or tobacco.