The Shotai Conspiracy (昌泰の変)
The Shotai Conspiracy (Shotai no hen in Japanese), which occurred in January 901, was a coup in which Emperor Daigo, acting on the false charges of FUJIWARA no Takahira, the Minister of the Left, against SUGAWARA no Michizane, the Minister of the Right, demoted Michizane and sent him into de facto exile to Dazaifu (an outpost in far off Kyushu) as Dazai Gon no Sochi (Deputy Commander of Dazaifu); also, Michizane's children as well as MINAMOTO no Yoshi, the Middle Captain of the Guardsmen of the Right, were either demoted or exiled.
In the general background of this event, the main reason for the conspiracy is considered to be the antagonism between Tokihira and Michizane, but there were other reasons as well.
Even after Retired Emperor Uda (who soon after became Cloistered Emperor Uta) abdicated the throne to Emperor Daigo, he went far beyond merely his written injunction, the Kanpyo goyuikai--which advised the new emperor on how to prepare himself to rule--and actively planned to continue his leadership role in the new emperor's government by surrounding Emperor Daigo with the group of his closest aides and ministers who had been the driving force behind the administration of the Kanpyo era, notably Michizane but also including MINAMOTO no Yoshi, the Chunagon (vice-councilor of state) MINAMOTO no Mare, the Kuroudo no kami (Majordomo of the palace) TAIRA no Suenaga, and the Jiju (Chamberlain) FUJIWARA no Tadahira. These efforts by Uda resulted in a strong backlash which was not limited only to high-ranking aristocrats like Tokihira and the Dainagon (chief councilor of state) MINAMOTO no Hikaru (a court noble) but extended to middle- and lower-ranking nobles like FUJIWARA no Kiyotsura, FUJIWARA no Sugane, and Kiyoyuki MIYOSHI as well. Eventually, when rumors began to fly that Cloistered Emperor Uda was going to raise Michizane's son-in-law, the Imperial Prince Tokiyo, to the rank of Kotaitei (one rank below the heir apparent), those who were nursing secret resentment against Uda and Michizane for their political maneuvers, including Emperor Daigo, FUJIWARA no Tokihira, and FUJIWARA no Sugane (the new Majordomo of the palace following TAIRA no Hidenaga's recent death by illness), began to plan how to recover control over the government.
In the coup, Michizane and Yoshi (who was demoted to vice-governor of Izumo Province) were purged from the government, and immediately after the coup MINAMOTO no Mare, who had managed to avoid any demotion or other penalty, died of illness, while in the same vein, FUJIWARA no Tadahira was--in truth if not in name--ousted from his vital role at the center of government, meaning the coup ended in a decisive political victory for Emperor Daigo and FUJIWARA no Tokihira's faction. The Emperor and Tokihira planned political reforms to put themselves in direct leadership roles for the new administration, which was called 'Engi no chi' (the (glorious) government during the Engi era), but only eight years after the coup, Tokihira died suddenly, and moreover Emperor Daigo became more and more prone to illness, which allowed de facto political power to shift back again under the control of Cloistered Emperor Uda and FUJIWARA no Tadahira.