- Titles: Tamba no kami
- Other Names: Miyazawa Heihachi
Kazumasa was a senior Asai retainer and a noted general who first distinguished himself in the service of Asai Sukemasa. In 1561 he relieved Sawayama Castle - under attack by the Rokkaku - and afterwards became the lord of that place. At the Battle of Anegawa in 1570 Kazumasa's favorite horse was shot out from under him, so he borrowed another and led a charge into the Oda army. His attack brushed aside troops under Shibata Katsuie and Hashiba (Toyotomi) Hideyoshi but were finally stopped by the units of Sakuma Nobumori and Mori Yoshinari before he reached Oda Nobunaga's headquarters. In 1573 Kazumasa's Sawayama Castle was besieged by almost 35,000 Oda troops and held out for nearly 8 months. Kazumasa surrendered when provisions finally ran out and his aged mother, a hostage with the Asai, was crucified on Asai Nagamasa's orders when the latter learned of the news. Nobunaga received Kazumasa cordially and gave him the Takashima District of western Ômi Province. In 1578 Kazumasa fled his fief for some unknown reason, and it is theorized that he spent his remaining days farming in Ômi Province.