Adachi Nagayasu (安達長泰)

Nagayasu ADACHI (1211 – September 26, 1262) was a gokenin (a shogunal retainer)of the Kamakura bakufu (Japanese feudal government headed by a shogun) in the early Kamakura period. He was a member of the Adachi clan and was a legitimate son of Tokinaga ADACHI. His common name was Taro. He was from the branch family of the Adachi clan and Nagayasu started to use the name Osone which was derived from his father's territory, Osone manor (Yamagata City), so he was also called Nagayasu OSONE. His son was Nagatsune ADACHI.

His first appearance in "Azuma Kagami" (The Mirror of the East) was in July, 1235, in the article telling that he played a role of holding a sword during a memorial service for the shogun in the main hall when he was 25. He was appointed as Saemon no jo (third-ranked officer of the Left Division of Outer Palace Guards) in 1245. In the Battle of Hoji in July, 1247, he departed for the front with the head family, Yoshikage ADACHI and so on, to attack the Miura clan. After the war, in September, he served as an envoy to explain the government's position to the Imperial Court, and in 1249, he raised himself to Hikitsukeshu (Coadjutor of the High Court). In 1254, he was appointed as Kazusa no suke (Assistant Governor of Kazusa Province). Since then, Kazusa no suke became a fixed post for the line of Osone clan.

On October 3, 1262, he died at the age of 52 ["Sonpibunmyaku" (a text compiled in the fourteenth century that records the lineages of the aristocracy)].