In 1177, he met with a number of others in secret in his mountain villa in Shishigatani (some sources, such as the Gukanshō, say the villa belonged to someone else), and plotted to overthrow Daijō Daijin Taira no Kiyomori who, along with other members of the Taira clan, dominated and controlled the Imperial government. The plot was discovered before any actual action was taken, and Shunkan was exiled, along with Fujiwara no Narichika, Narichika's son Fujiwara no Naritsune, and Taira no Yasunori, to an island called Kikai-ga-shima, south of Kyūshū's Satsuma province. There is debate as to whether or not this was the same place as the island bearing the name Kikai today.
Later that year, according to the Heike monogatari, when the Imperial consort Taira no Tokuko was pregnant with the future Emperor Antoku and was having difficulties, Kiyomori, her father, granted amnesty to Yasuyori and Naritsune, in order to appease their angry spirits, in the hopes of easing his daughter's pain. Shunkan was thus left alone on the island, the fourth exile Narichika having been executed by the Taira some time before.
He was found two years later, in 1179, by a monk from his temple by the name of Ariō, who brought a letter from his (Ariō's) daughter. Having already sunk into deep despair during his time alone on the island, Shunkan read the letter and made the decision to commit suicide. He refused food, and died of starvation. Ariō then brought the monk's ashes and bones back to the capital.