|Died||4 January 1966 (aged 67)
|Notable students||Motokatsu Inoue, Mabuni Kenwa, Fujitani Masatoshi, Tomisaburo Wakayama, Manzo Iwata|
Isamu Fujita was born in Tokyo, and studied Kōga-ryū Wada Ha (Kōga-ryū Ninjutsu) with his grandfather Fujita Shintazaemon, 13th Soke of the Kōga-ryū. He studied at Waseda and Meiji Universities, and after leaving school, worked at a newspaper company. He went on to study several other martial arts and was also noted as an author, researcher and collector of ancient scrolls. According to some references, "opinions are divided if he was a real ninja or a mere budō researcher."
During World War II, Fujita taught strategy in the Army Academy of Nakano (Rikugun Nakano Gakkō). Fujita later worked as a government security specialist. In later years he was influential in teaching many traditional Japanese arts. Notable students include Motokatsu Inoue, Mabuni Kenwa, Fujitani Masatoshi, actor Tomisaburo Wakayama and Manzo Iwata, who became heir to some of his styles. Fujita left no heir for Kōga-ryū Wada Ha.
Fujita Seiko published Zukai Torinawajutsu showing hundreds of Hojōjutsu ties from many different schools, and several other texts on ninjutsu and martial arts. He died of cirrhosis of the liver at about the age of 68 and likely suffered from hereditary angioedema (which can preclude the practice of martial arts, although Fujita may have demonstrated the ability to overcome some disease symptoms). His collection, the Fujita Seiko Bunko, is housed at Iga-Ueno Museum, Odawara Castle.
- Draeger, Donn F.; Smith, Robert W. (1980). Comprehensive Asian fighting arts. Kodansha International. pp. 130–131. Retrieved 18 April 2012.
- "Fujita Seiko (1899-1966) | Martial Antiques". Ryukyu-bugei.com. 2011-04-09. Retrieved 2014-01-18.
- Ashrafian, Hutan. (2005). "Hereditary angioedema in a martial arts family". Clin J Sport Med 15: 277–8. doi:10.1097/01.jsm.0000171884.12174.6a.
- "Fujita Seiko (Isamu Fujita) – The Last Koga Ninja". Retrieved 18 April 2012.
- Fujita Seiko:: The Last Koga Ninja by Phillip T. Hevener (19 February 2008) ISBN 978-1436301763