FUJIWARA no Sumitomo, who was ranked Jushichiinoge (Junior Seventh Rank, Lower Grade) and served as Governor of Iyo Province, was responsible for combatting pirates, but it is said that in approximately 936, he became the leader of a band of pirates based on Hiburi Island in Iyo Province, commanding a fleet of 1,000 boats.
従七位下伊予国掾の藤原純友は海賊の討伐に当たっていたが、承平6年（936年）頃には伊予国日振島を根拠に1000艘を組織する海賊の頭目となっていたとされる。