There is an interesting article by Koryū practitioner and researcher - Ellis Amdur entitle 'How Many Generations Does It Take To Create A Ryūha' (see link below), in which he examines the history of the Yōshin-ryū Jūjutsu (楊心流柔術) and suggests that its founder - Akiyama Shirobei Yoshitoki (秋山四朗兵衛義時) may not have existed.

However, an Oe Senri (大江千兵) is listed as the 2nd head of the Yōshin-ryū, is shown as inheriting the Yōshin-ryū from Akiyama and thus becoming the 2nd head. Amdur suggests that if Akiyama had of existed it would have been more usual for the Yōshin-ryū to have been passed down through his own family.

Instead Amdur surmises that the school was created by Oe Senri Hirotomi (大江千兵衛広富) aka Oe Senri Yoshitoki（大江専兵衛義時) after having studied a local school called Miura Yōshin-Koryū (三浦楊心古流 - willow hearted old school) founded by Nakamura Sakyodayu Yoshikuni in Miura village in the area of Nagasaki. This was allegedly formed from Chinese martial arts, medicine and a family Jūjutsu school which had been founded by Sakyodayu’s grandfather Nakamura Yorifusa.

Another suggestion is that as Nakamura Sakyodayu was a retainer of Takeda Koshu and as Takeda had founded a school called Taiyo-ryū ,that it was that school that Yoshikuni learned. However, it seems that Oe Senri learned from Yoshikuni, but may not have received a licence in that school.

Martial arts researcher - Watatani Kiyoshi (綿谷雪) throws further doubt on the story of Akiyama Shirobei Yoshitoki travelling to China to study martial arts and medicine, because travel to China was not permitted at that time. It seems that the China story only gained currency in the writings of the Tenjin Shin'yō-ryū school (derived from the Yōshin-ryū and Shin no Shindo-ryū Jūjutsu schools) many years later.

There have also been observations raised that Oe Senri shared the same name Yoshitoki with Akiyama.

Although there is doubt regarding the existence of Akiyama and the China travel story, there was a source of Chinese Kenpo in the Nagasaki area and that was Miura Yoshitatsu (三浦義辰創), who had founded the Miura-ryū (三浦流柔術).

Amadur makes the suggestion that Oe Sanri studied under under Miura Yoshitatsu, but may not have reached licence level and thus invented Akiyama so as to provide himself with the illusion of legitimacy when he founded the (Akiyama) Yōshin-ryū.

As such the Chinese Kenpō techniques of Yōshin-ryū would have not come from the Akiyama (who probably didn’t exist), but rather they would have come from the same source as those contained within the Ryōi Shintō-ryū, that is Chin Genpin via the Miura-ryū.

If that were to be the case then as Miura was a student of Fukuno’s Ryōi Shintō-ryū, that would mean that the Ryōi Shintō-ryū was the ancestor of all of the Yoshin-ryū lines including Tenjin Shin’yo-ryū, Shin no Shindo-ryū, Totsuka-ha Yōshin-ryū -ryū and even Wadō-ryū Karate

Furthermore, this would mean that both of the Jūjutsu schools that formed the twin pillars of the foundation of Kōdōkan Judo (Kito-ryū and Tenjin Shin’yo-ryū), both trace their origins back to Ryōi Shintō-ryū. Thus, the origins of Jūdō would be found entirely found in Ryōi Shintō-ryū derived traditions.

In the early 19th century, when the Jigo Tenshin-ryū (aka Ise Jitoku Tenshin-ryū - a derivative school of Ryōi Shintō-ryū) was founded and included the Yōshin-ryū ‘Sakkatsu’ (killing & revival techniques) within its core Ryōi Shintō-ryū curriculum, they probably did not realise that these were not new, but rather they were just returning home.

The illustrations above are:

Part of the - Yōshin-ryū Jūjutsu Sakkatsu (killing & living) menjō (licence) (楊心流柔術殺活免状) - from the author's collection

Kyushō from Yōshin-ryū Jūjutsu Shikatsu-den (life & death) no maki (scroll) (楊心流柔術死活伝之巻) - recently sold on a Japanese auction site.

Ellis Amdur's article can be found at: https://kogenbudo.org/how-many-generations-does-it-take-to-create-a-ryuha/?fbclid=IwAR1gUoAn4LyH1yDh92gzId_nQGNbDl04rpprGu5JfvJit5IH5hESrFej6-Q