The mitchoku was kept secret from the Tokugawa gosanke and gosankyo (three privileged branches of Tokugawa family) other than the Mito Domain but the copies of it were sent to other related daimyo (Japanese feudal lord) through Sekke (line of regents and advisers) except Kanpaku.
水戸藩以外の徳川御三家、御三卿などには秘匿されていたが、写しは関白以外の摂家を通じて縁家の大名に送付された。