In November 2017, “Somanaka Kimura Honke Documents（杣中木村本家文書）” was found. By comparing the other historical documents, this paper will clarify the process of formation, service, family finances, economy, and espionage activities of “Koka-five-ninja（甲賀五人）” served the Owari clan. There were seventeen Koka ninja in the Owari clan, but they were dismissed, and “Koka-five-ninja” were established after the employment of Kimura Okunosuke, in 1672. Okunosuke visited Koka and made a contract with “Koka-five-ninja,” they inherit ninjutsu called “Kagun （家軍）.” When “Koka-five-ninja” came to Nagoya for target practice, Okunosuke went to visit them at their inn, and when there was an inheritance, he and his son went to Koka to participate the ceremony. Okunosuke had to pay for high cost of living in Nagoya and “Koka-five-ninja” staying at his home, and he became impoverished. The first Okunosuke might be cautious about intelligence activities. The intelligence activities of “Kokafive- ninja” were active only for 16 years, from 1723 to 1739, after Okunosuke’s death.

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[in Japanese]

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The purpose of this paper is to examine the succession and supply sources of ninjas by taking up the Honda clan as an example of research on ninja family succession. The basic historical material used was the “Honda-ke Okazaki-han Bungencho,” a collection of ancestral writings of vassals who served the Honda clan. From the analysis results of this book, it became clear that （00 years after the start of the succession, it was impossible for even the ninja family to survive without the succession by adoptive children, just like a general samurai. In addition, it was found that there were many cases where ninjas were transferred to other departments due to role changes, and it became clear that it was difficult to continue to inherit the duties of ninjas. 　A study on the source of ninja revealed that many of the ninja who served the Honda clan were recruited from Mikawa Province, the hometown of Honda Tadakatsu, the Honda clan’s transfer territory, and the former territory. In addition, it was newly found that many of the adopted children of ninjas were from Ashigaru, Doshin, and the sons of their colleagues.

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