Born in 1522 as the son of Iwatsuki Castle lord Ota Suketane, he seized the vacant Iwatsuki Castle by force in 1547 after his brother Sukeaki's death, though he briefly submitted to the Later Hojo in 1548. Allying with Uesugi Kenshin, he made Iwatsuki the center of anti-Hojo resistance in the region. In 1564, after being defeated at the Second Battle of Konodai while reinforcing the Satomi clan, his pro-Hojo eldest son Ota Ujisuke seized the castle in his absence and expelled him. He subsequently served the Utsunomiya of Shimotsuke and then Satake Yoshishige of Hitachi, holding Katano Castle as a base for continued anti-Hojo resistance. He joined the 1590 Siege of Odawara and had an audience with Toyotomi Hideyoshi, but never regained his homeland, dying at Katano Castle in 1591.

A resolute and shrewd strategist who cultivated independent ties with powerful figures like Uesugi Kenshin and Oda Nobunaga. Even after his expulsion, he never abandoned his anti-Hojo cause, embodying tenacious persistence.

Remembered as the Sengoku-era warlord who single-handedly built an anti-Hojo power base around Iwatsuki Castle. His dramatic downfall—expelled by his own son Ujisuke—stands as an emblematic tale of the power struggles that defined Kanto during the Sengoku period.