Not sure how much help this will be, but my aikido instructor is a student of Taisha ryu (and perhaps menkyo kaiden, but I'm not certain about that). He studied it in Hitoyoshi, in the southern part of Kyushu (he currently lives and teaches in Kumamoto City). He's told me just a bit about Taisha ryu at enkais and whatnot, but not much. He mentioned that it had some relationship with Yagyu Shinkage ryu, but I'm unclear exactly what that entailed. He also mentioned that, like Yagyu Shinkage ryu, Taisha ryu at one point had some sort of ninja connection on its "ura" side. The exact way he put it was "Omote wa...kenjutsu. Ura wa...ninja." That's about all I was able to drag out of him, sorry it's not much. I also asked if he taught Taisha ryu, but he was quite clear that he did not and did not wish to. At that point I decided to stop being nosy and enjoy a more upbeat discussion on aikido with him. (to all Yagyu Shinkage ryu practitioners, please don't take offense. It's quite possible I misunderstood what was said regarding Yagyu Shinkage ryu and if so, I humbly apologize).