Minamoto no Yorimasa (源頼政, 1106-1180), also known as "Gensanmi Yorimasa," was a samurai of the Minamoto clan and the leader of the clan's armies at the beginning of the Gempei War. His suicide by seppuku remains famous, and is considered to have paved the way for this practice.
More of a poet than a warrior, Yorimasa tried throughout his life to stay out of the decades-long struggles between the Minamoto and Taira clans, and avoided choosing sides, even being friends with Taira no Kiyomori at one time.
During the Heiji Rebellion of 1160, having sided with the withdrawn emperor Go-Shirakawa as he had already done in 1156 during the Hōgen Rebellion, he tipped the scales just enough in favor of the Taira to enable them to overthrow the Minamoto.
However, when he officially retired from service in Kiyomori's army in 1179, he began to change his mind about opposing his own clan, especially since relations between Go-Shirakawa and Kiyomori had become very strained and Kiyomori had the former emperor arrested, causing strong anti-Taira opposition as well.
On March 21, 1180, Taira no Kiyomori put on the imperial throne his grandson Antoku, then only two years old, after the abdication of emperor Takakura.
Prince Mochihito, son of Go-Shirakawa, felt that he had been deprived of his place on the throne and Yorimasa pushed him to launch on May 5 a call to arms to the various samurai families and to the Buddhist monasteries that Kiyomori had offended.
The Genpei war officially started with the first battle of Uji, on June 23. Yorimasa led Minamoto troops, accompanied by sōhei (monk-warriors) from the Mii-dera, to defend the Byōdō-in where the prince had taken refuge.
Despite the fact that the monks had removed the planks of the bridge leading to the temple, the Taira manage to get past the defenses.
Yorimasa tries to help the prince escape, but is wounded by an arrow. To avoid being captured by the enemy, he then performs seppuku in the Phoenix Hall: he first writes a farewell poem on the back of his banner, before taking his dagger and cutting open his abdomen.
This is one of the first known seppukus and the one that codified the procedure for the following ones. Prince Mochihito managed to escape towards Nara, but was killed a few days later by Taira warriors.
Minamoto no Yorimasa's poems have been collected in the anthology Yorimasa Kashū, as well as in the imperial anthologies Shin kokin-shū and Senzai wakashū.
His daughter, Nijō-in no Sanuki, was also a poet.
A legend from the Heike monogatari states that in 1153, Yorimasa is said to have killed with arrows a nude that landed on the roof of the imperial palace.