So, basically what set me on this path of looking for documentation or writings by Gensai is that his unique form of kendo, Gensai-Ryu, is a lost art form now. I figured that “recreating” it could be possible or creating something that fits the descriptions of its style might be possible if I could find access to physical descriptions on him (such as his fighting stance, how he held his sword, etc), as well as what kendo styles he studied in particular to develop it, as he had used already pre-existing sword styles to create it. If I had access to, say, the styles most practiced or taught by his original teacher, that might give me a good idea, but he’s basically scrubbed from history in everything other than name it seems. Perhaps there is more useful information on Japanese internet?