However Masakado sent proof that came from five Kokufu (provincial office) of Hitachi Province, Shimosa Province, Shimotsuke Province, Musashi Province, Kozuke Province, dated May 28, 939, to Dajo daijin (imperial regent and grand minister), FUJIWARA no Tadahira, in which said 'there was no proof that there was a plan to plot treason,' then Masakado's pleading was accepted, on the other hand, Tsunemoto was detained in Left division of palace gate guards for punishment of his slander.
しかし将門らが承平9年5月2日付けで常陸国・下総国・下野国・武蔵国・上野国5カ国の国府の「謀反は事実無根」との証明書を太政大臣藤原忠平へ送ると、将門らはその申し開きが認められ、逆に経基は讒言の罪によって左衛門府に拘禁されてしまった。