Hi,
Tanemura Sensei claims the Soke-ship in 26 arts via a number of means, including the formation of his own branches (Tanemura-ha) of many of the Bujinkan arts, such as Togakure Ryu, Gyokko Ryu, Koto Ryu etc after leaving Hatsumi Sensei and forming the Genbukan; the splitting of the various branches of Kukishin Ryuha (Kukishinden Happo Biken, Kukishin Ryu Bojutsu, Hontai Kukishin Ryu, Shinden Tatara Ryu, Kijin Chosui Ryu etc); and Ryuha obtained from other teachers, such as Kimura Sensei, Ueno Sensei, and Sato Sensei. These include Asayama Ichiden Ryu, Bokuden Ryu, Yagyu Shingan Ryu Katchu Yawara, Tenshin Koryu, and the Chinese systems.
From all reports, after splitting with Hatsumi Sensei, Tanemura Sensei spent a number of years seeking out former students and training partners of Takamatsu Sensei, and learned everything he could from them.
I may have missed out a bit, or gotten one or two things mixed up, Genbukan/KJJR guys, please correct anything you feel I have erred on.