It is not known exactly when the relationship between Mitsuhiro KARASUMARU and Ryosa began, but it is clear from "Otekagami (a collection of calligraphy, imperial correspondence, and other works dating from the Heian through the Muromachi periods)", "kohitsumeiyo shu (collection of pieces of old writings)" and "Meikanshu (collection of Meikan)" that Ryosa learned the art of appraisal of old writings from Mitsuhiro.
烏丸光広と了佐の交友がいつから始まったのか定かでないが、了佐が光広に古筆鑑定の方法を学んだことは、『御手鑑』、『古筆名葉集』、『明翰集』などから知られる。