Dazai no sochi (also known as Dazai no sotsu) (Head of Dazaifu) (大宰帥)
Dazai no sochi was the head of Dazaifu. Under the Ritsuryo legal system, Dazai no sochi was the position responsible for diplomacy and defense in Kyushu, ruling nine ryoseikoku provinces and two islands in Saikaido in Kyushu. Its undersecretary was Dazai Gonnosochi or Dazai Daini.
There are several opinions about the origin of Dazai no sochi such as Tsukushi Ohomikotomochi (also known as Tsukushi Taisai) that was the position to supervise the Natsunomiyake family; a kingdom in Kyushu; and Tsukushi Totokufu in the Tang dynasty, but it is commonly accepted that SOGA no Himuka was appointed Tsukushi no sochi, which was the beginning of Dazai no sochi, though Tsukushi no sochi was renamed Tsukushi no Soryo later.
After the Taiho ritsuryo legal code was enacted, the title 'Dazai no sochi' was established and the Imperial Prince at Third Rank or Fourth Rank or the retainer at Junior Third Rank or sometimes Senior Third Rank were appointed. In the beginning, Dazai no sochi sometimes worked as a stepping stone to Dainagon or above as can be seen in the example of OOTOMO no Tabito. TAJIHI no Miyakemaro in the Konin era was the last case to use Dazai no sochi as a stepping stone to a higher position. As Sangi and Chunagon were concurrently appointed Dazai no sochi at that time, some officials abused this situation so as to avoid going to Dazaifu on the pretext of the importance of their duty at a position other than Dazai no sochi so that they received seasonal stipends and untaxed lands as absentee officials.
As Imperial Prince Iyo, a son of Emperor Kanmu, was appointed to Dazai no sochi as an absentee official in 806, and the land system Kueiden was introduced in the district of Dazaifu in 823, it became a practice that the Imperial Prince (Imperial Prince Kazuwara at that time) was appointed Dazai no sochi just like Shinoninkoku and called 'Sochinomiya.'
Dazai Gonnosochi or Daini was selected from the retainers of the appointee and dispatched as de facto governor (Gonnosochi was dispatched for the appointee at the rank of Chunagon, and Daini was dispatched for the rank of Sangi).
Unlike the case of Shinoninkoku, Dazai no sochi was established merely in customary law and not in the ritsuryo nor kyakushiki; therefore, sometimes persons not from the Imperial family were appointed Dazai no sochi. Examples of that kind of Dazai no sochi are, TAIRA no Korenaka who was appointed in 1001 as an imperial person refused to be a successor to FUJIWARA no Korechika who had been demoted (exiled in fact) to Gonnosochi, and FUJIWARA no Takasue who was appointed in 1179 as a supervisor of Gonnosochi FUJIWARA no Motofusa who was demoted to Gonnosochi (but as Motofusa was exiled to Bizen province in fact, Takasue's appointment of Dazai no sochi was canceled).
It is considered that, after the invasion of northern Kyushu by Toi in 1019, Dazai no sochi including Sochinomiya mostly ceased to go to Dazaifu with a few exceptions for fear that the Imperial Prince as Dazai no sochi would be blamed for invasion. The appointment of Dazai no sochi continued even after the position became merely nominal until the reform of official system in 1869. The last Dazai no sochi was Prince Arisugawa Taruhito.