Prince Okiyo (興世王)
Prince Okiyo (? - 940) was a member of the Imperial Family in the mid-Heian period. There is a theory that he was the fourth-generation descendant of Imperial Prince Iyo, the third prince of Emperor Kanmu, but this theory lacks credibility because it is based on a family tree made during the Meiji period. It seems that he assumed the post of Zuryo (the head of the provincial governors) in various districts successively, but the details were not clear. He was one of the masterminds of the Johei and Tengyo War. He was the Musashi-no-kuni Gon-no-kami (Substitute Provisional Governor of Musashi Province) with the court rank of Jugoinoge (Junior Fifth Rank, Lower Grade) and also the Kazusa no suke (Assistant Governor of Kazusa Province) appointed by TAIRA no Masakado.
He arrived in Musashi Province as kokushi (provincial governors) (Gon-no-kami, substitute for Kami, the Governor) in 938. Immediately after his arrival, he conducted a land survey with MINAMOTO no Tsunemoto, an officer of Musashi Province. However, MUSASHI no Takeshiba, the local magistrate of Adachi County, refused the Gon-no-kami's land survey because Adachi County had decided not to conduct the survey in the customary way unless the official Governor arrived in the county. In response, Prince Okiyo and Tsunemoto sent troops and gave orders to attack and sack Takeshiba's office. Takeshiba ran away to the fields and mountains, requesting the restoration of his property in writing; however, Prince Okiyo not only refused his request but also threatened Takeshiba by showing him the battle preparations that had been made. TAIRA no Masakado, who visited Takeshiba with his troops after learning of the dispute, settled the problem peacefully by arranging a meeting between Prince Okiyo and Takeshiba. However, Tsunemoto's quarters were besieged by the Takeshiba's troops in the midst of the feast, with the result that Tsunemoto, feeling a threat to his life, hastily returned to Kyoto. Accepting the complaints of appeal by Tsunemoto that Prince Okiyo, Takeshiba and Masakado were plotting a rebellion in conspiracy, Daijo daijin (Grand Minister of State) FUJIWARA no Tadahira, Masakado's lord, sent an envoy to Togoku (the eastern part of Japan, particularly the Kanto region) after issuing a migyosho (documents for informing of decisions made by third or upper ranked authorities) to investigate whether the complaints were true. The certifications sent by Prince Okiyo, Masakado and Takeshiba dated May 2, 939, dispelled the court's doubts because the provincial office of five provinces--Hitachi, Shimofusa, Shimotsuke, Musashi and Kozuke--suggested in the certification that the rumor of a planned rebellion was groundless. To the contrary, Tsunemoto was confined to the Saemon-no-fu (office of the Imperial Police) for libel.
However, things suddenly turned after the arrival in the province of Governor Sadafusa (Prince Kudara) in May of the same year, 939. Because Prince Okiyo and Sadafusa were at odds, Sadafusa forcibly excluded Prince Okiyo from the conferences held at the provincial office. Prince Okiyo soon left the area of appointment and stayed with Masakado in Shimofusa Province. The following year, when a confrontation arose between FUJIWARA no Haruaki, a powerful regional clan in Hitachi Province, and FUJIWARA no Korechika, the Hitachi no suke (Assistant Governor of Hitachi Province), Masakado, assisting Haruaki, attacked the Hitachi provincial office and occupied it. After Masakado deprived Korechika of the provincial seal, he sent Korechika back to Kyoto. Prince Okiyo, who had been Masakado's close adviser, said to him, 'Considering the current situation, your responsibility is not light even if you insist that you occupied only one province.
Then you should occupy not only one province but also the whole area of Banto (Togoku).'
Thus he recommended that Makakado conquer the Togoku. Adopting Prince Okiyo's advice, Masakado occupied the provincial offices of Shimonotsuke and Kozuke provinces, in what came to be called the Johei and Tengyo War. Under Masakado, who named himself the new emperor at the Kozuke provincial office, Prince Okiyo, who became the most influential person at that time, issued the Jimoku (ceremony for appointment of officials) in his own right with FUJIWARA no Harumochi, being appointed as the Assistant Governor of Kazusa Province.
With the rebellion by Masakado etc., Tsunemoto was acquitted the following year, in 940, because his past appeal became a fact. The court ordered that a force be sent to punish Masakado. Masakado died in the battle against TAIRA no Sadamori and FUJIWARA no Hidesato on February 14 of the same year, 940, whereupon his influence immediately ceased. The masterminds of the rebellion were killed one after the other, including Prince Okiyo, who was killed by FUJIWARA no Kinmasa in Kazusa Province on February 19.