EDIT: This is the same concept as Seiga Kaku and Seiga Nyan-Nyan. Kasen's full name is Kasen Ibaraki and her hermit name is Ibarakasen/Ibaraka-sen.
Oh, I recall she was referred to as Kasen Ibara last time I visited Touhou wiki. Glad to see that rectified. I didn't know Ibarakasen was Kasen's hermit name though.