Hi Volker,
You seem to know a great deal about Kajiyama Yasutoshi’s work. My grandfather passed away in 2014 and he left a very beutiful sword after him. I have searched for information about the sword since then and just recently understood that this sword is probably made by Kajiyama Yasutoshi based on the signature on the tang. If you would like to know more or could help with more information that would be fantastic. See the bad copy of the tang signature.
cheers,
Fredrik