As concerns a link between Mitose and Fujita, Ninjutsu, Nanban Satto Ryu Kenpo, or anything else, I would have to agree with Don that there is neither evidence of a connection, nor evidence that Mitose himself actaully made this claim. I have done extensive information into the career of Fujita Seiko, and even established a relationship through both research and practice with Fujita's inheritors, via the line of Iwata Manzo, Fujita's uchi-deshi.
In the course of my research I never found a single mention of Mitose in Fujita's works, or the recollections of his acknowledged students. I have personally had the honour of being the uke of, and interviewing Murayama Kunio, Iwata Manzo's uchi-deshi from 1968-1970, and he had no knowledge of the Mitose claims, which is interesting, as the other stories Iwata Manzo told him, match the statements of the Bugei Ryuha Daijiten and Fujita's obituary, which I have posted on my research site,
http://fujitaseiko.tripod.com.
This obituary was passed onto me by Sam Moldezki, a senior student of Murayama Kunio and Iwata Genzo, Iwata Manzo's son. The original of the obituary is in Iwata Genzo's possession, as it was cut out by Iwata Manzo to commemorate his teacher's funeral. Iwata Genzo inherited all of Fujita's living arts(Wada-Ha Koga Ryu is not among them) when his father, Iwata Manzo died in 1993. This fact is attested to by The Nihon Kobudo Shinkokai, at which both Iwata's demonstrated Nanban Satto Ryu Kenpo during the 1990's.
Lastly, having had the good fortune to be uke at four separate Nanban Satto Ryu seminars, I can say that the skills shown in Mitose's books look nothing like them. Satto Ryu is a system that contains Kansetsu Waza (locks) Nage Waza (throws) and Atemi Waza (pressure point attacks) and is related to Nanban Ippon Ryu. The Bugei Ryuha Daijiten (pg 662) lists the lineage as follows: Hashimoto Ippusai (1)-Hashimoto Ippusai (2)-Fujita Seiko (1919)-Iwata Manzo (1948) The Nihon Kobudo Taikai: All of the above, plus Iwata Genzo (1993)