Osada Tadamune (長田忠致)
He was descended from the Kanmu-Heishi (a branch of the Taira clan), and according to "Sonpi Bunmyaku (a text compiled in the fourteenth century that records the lineages of the aristocracy)", he was the goseimago (the son of great-great-grandchild) of TAIRA no Muneyori who was one of the FUJIWARA no Michinaga Shitenno (the big four retainers of FUJIWARA no Michinaga). He was based in Noma, Owari Province, and was working for Genji (the Minamoto clan) during the Heiji era (1159-1160). In 1159, MINAMOTO no Yoshitomo defeated in the Heiji War and was escaping to Togoku (the eastern part of Japan, particularly Kanto region) put himself under the protection of Tadamune, who was the father-in-law of Masakiyo Kamata, a person accompanying him at that time. However, Tadamune and his son, Kagemune, trapped Yoshitomo and killed him in a bathroom for a reward from Heike (the Taira family), and offered the head of Yoshitomo to TAIRA no Kiyomori in Rokuhara. Masakiyo was also killed at the time, the daughter of Tadamune (the wife of Masakiyo) is said to have committed suicide by throwing herself into the river due to great sorrow.
Tadamune, who was appointed as Iki no kuni no Kami (Governor of Iki Province) in return for the assassination of Yoshitomo, expressed open dissatisfaction with the reward and complained 'I deserve the position of Sama no kami (Captain of Samaryo, Left Division of Bureau of Horses) or at least Kokushi (provincial governor) of Mino Province or Owari Province,' but allegedly, he hastily withdrew the complaint later because he was about to be punished by Kiyomori who was offended by the remark. His disgraceful behavior is described in "Heiji Monogatari" (The Tale of the Heiji) in a totally critical tone.
Later, when MINAMOTO no Yoritomo raised his army, Tadamune joined his side. Yoritomo generously told Tadamune, who had committed the serious sin of killing Yoritomo's real father, 'If you work hard, I'll give you Mino-Owari (meaning Mino and Owari Provinces),' Tadamune worked hard believing in his word. However, when Yoritomo came into power after Heike (the Taira family) was searched out and destroyed, Tadamune came to be accused as an enemy who murdered Yoritomo's father after all, and he was allegedly killed on the orders of Yoritomo at last.
According to a legend, Yoritomo told Tadamune 'As promised, I will give you Mino-Owari' when he was killed (The word "Mino-Owari" has double meaning here, the word basically means "Mino and Owari Provinces," but it also means "the end of your life" with the same pronunciation when spelled differently in Japanese.)
The date and the place of the execution of Tadamune and his attitude at that time are unclear because there are several stories about them, but according to "Horyakukanki" (A History Book of the 14th century in Japan), Tadamune was beheaded in Mino Province in October 1190 when Yoritomo went to the capital (Kyoto).
It is said that his surviving descendents subsequently escaped to the south of Mikawa Province (present-day Tanao District, Hekinan City) and they worked hard on learning Western medicine by utilizing their intellect in later generations. Incidentally, Naokatsu NAGAI who actively worked as a retainer of Ieyasu TOKUGAWA in the Sengoku period (the period of warring states) was a descendent of Tadamune OSADA, and it is said that he changed his surname to NAGAI on the order of Ieyasu who hated his original surname, OSADA. One legend suggests that the surviving descendents of Tadamune OSADA escaped to Kai Province (present-day Yamanashi Prefecture), and it is said that the Osada family still exists in Yamanashi Prefecture.