Re: Yoseikan katas
I haven't much more information in addition to David's ones. Now I speculate about the origins of these kata. Probably they were created in recent times. The fact could be corroborated by their presence in Nihon den Jujutsu but in no other Mochizuki sensei's text. In addition these katas were ideated more to remember techniques arranged in series than to transmit some priciples (like in Hyori no kata or Tai Sabaki no kata).
I think they are important, but in a lesser way than the main katas and this can be justified by the fact that all the techniques were also taught as separate in the more conservative approach of the old Yoseikan Aiki