The Kashima Shinryu swordwork seems to be very much associated with the Yamaguchi "school", even if he himself never studied it formally. I went to a summer school in Belgium in the late 1980s with Yasuno Shihan from the Hombu Dojo, whom I knew to have been a student of Yamaguchi Sensei. We spent half an hour or so practising bokken kesagiri (the ichi-no-dachi of the Kashima kihon-dachi), which seemed rather unfamiliar to many of those in the class.
Absolutely. It was Mr Sekiya who taught Kanetsuka Shihan those basic sword moves at Ryushinkan. I was a Ryushinkan member at the time and such practice was usually done at lunchtime. Old students like David Helsby still practice them. Yasuno Shihan had a close relationship with YS and married into the Yamaguchi family. When I stated that he never studied it formally, I mean that he never enrolled as a student of Kunii Zenya.