Azai Koreyasu served as a bushō and retainer of the Azai clan based in northern Ōmi Province.
Koreyasu served as an attendant for Azai Hisamasa, the head of the Azai clan. He continued to serve in this role after Hisamasa’s retirement in 1560. Koreyasu resided in the fukuju citadel of Odani Castle, a mountain castle in the Azai District of Ōmi. In 1573, he defended the kyōgoku citadel in the Siege of Odani Castle by a major contingent under the command of Oda Nobunaga. After moving to the komaru, or minor citadel, he served the dutiful role of kaishaku, beheading his lord, Hisamasa, before taking his own life. His children and grandchildren safely escaped to Mino Province.