I understand that the web site is a bit odd, but if you're really bull-headed like I am, you can track the links.this page
states that the dojo is a representative of "YAGYU SHINGAN RYU HYOHO IAI JUTSU". It also shows a scroll reading "Yagyu Shingan Ryu Hyoho Iai Jutsu", painted by Ishihara Masao, "one of Viol Shihan's Instructors".
If you look at the photo captioned "John M. Viol Shihan receives Menkyo Kaiden in Japan - 1991" on this page
and then look at the gallery of John Viol's instructors
, you can see that the person in the photo for the menkyo kaiden is also in other pictures and identified as Ishihara Masao.
Considering the other pictures and statements lead us to believe he also studied Toyama Ryu under Nakamura Taizaburo, his claims to teaching a sogobujutsu seem to relate to Yagyu Shingan Ryu, at least to me. It may be a confusing web site, but I'm still pretty sure that it does in fact list his styles and teachers, you just have to wade through some weird things to get to them.