It's quite a bit more complicated than that. There were myriads of political action groups. It is unclear to me if they were formed, one after another, often by the same personages, because:
1. Each had a specific goal
2. The leaders thought that the group had become "played out" with too many hangers-on, so they would create a newer more exclusive group, which would, in their view, fall prey to the same issues.
3. Different personages each wanted their own group to lead.
Anyway, they were as common as mushrooms on the forest floor.
Sure, the circles that Ueshiba ran in were actually quite small when you start tracking things down.
Toyama Mitsuru (who was, btw, connected to Tempu Nakamura) had his fingers into Manchuria before the Sakurakai came around. The Sakurakai was focused on Manchuria - and Ueshiba had his own interests there, of course.
Reminds me of one of Gozo Shioda's stories of his time in China - apparently the rumor going around in Japan was that he had been sent to China on a secret mission to assasinate a Chinese government minister.