Zenso Seyakuin was born in 1526 in Omi Province (Mie Prefecture), Japan. His family name is also pronounced Yakuin. He was a descent 17 generations removed of Masatada Tamba, noted physician. His father was Priest Sochu, who held the title of Hoin. His father died when he was a child.
Zenso Seyakuin went to Mount Hiei and became a priest. He soon returned to secular life and studied medicine under Dosan Manase, noted physician, and became one of his most distinguished disciples. He called himself Tokuunken and Yakujuin Hoin.
Much favored by Hideyoshi Toyotomi, he was Hideyoshi's adviser even on political affairs. The Enryakuji Temple on Mount Hiei was saved by Hideyoshi from destruction because of his advice.
The grateful priests made Zenso the founder of the Yakujuin Temple which was built in his honor. He was given the rank of Hoin (1585) and was appointed Yakuinshi, or chief of charity dispensary of the Court. Before Zenso's time, the charity dispensary was only a nominal institution. He and Hideyoshi revived it as a true charity institution and made medical aid available to poor people.
