Onami-hime

Onami-hime (1541-1602) was born as the daughter of Date Harumune, lord of Yonezawa Castle in Dewa. She was the elder sister of Date Terumune, father of Date Masamune, and so she was Masamune's aunt. She married Nikaidō Moriyoshi, lord of Sukagawa Castle in Mutsu, becoming his principal wife, and in 1561 (Eiroku 4) she gave birth to their eldest son, Heishirō. Heishirō was later adopted into the Ashina clan and became Ashina Moritaka, the 18th head of the Ashina house. In 1570 (Genki 1) she gave birth to a second son, Yukichika, and when her husband Moriyoshi died of illness in 1581 (Tenshō 9), Onami-hime took Buddhist vows and adopted the name Daijō-in. The family headship passed to this Yukichika while he was still a child, but in 1582 (Tenshō 10) he died young at the age of 13, and from then on Onami-hime is said to have taken direct control of the Sukagawa domain herself, governing the Nikaidō house as a de facto female castle lord. The Nikaidō clan was a mid-sized local lord house caught between two great powers, the Ashina clan of Aizu and the Date clan of Yonezawa, and it had maintained its independence through marriage policy and diplomacy. Onami-hime's period of rule also lay along the extension of that precarious balance, and she is thought to have been the linchpin of that diplomacy herself.

In 1589 (Tenshō 17), Date Masamune, who had destroyed the Ashina clan at the Battle of Suriagehara, pressed his momentum and launched an invasion of Sukagawa Castle in the Nikaidō domain, which was ruled by his aunt Onami-hime. Masamune is said to have repeatedly called for peace and surrender on the grounds of their kinship, but Onami-hime is reported to have rejected this and continued to resist. While many of the surrounding local lords submitted to Masamune, Sukagawa Castle alone ended up holding out to the very end. In the end Sukagawa Castle fell, partly due to the secret collusion of its retainers, and the Nikaidō house effectively ceased to exist. However, it should be noted that many of the specific exchanges in the peace negotiations, and the anecdotes told as the princess's own words in firmly rejecting Masamune's appeals, are based on war chronicles, regional gazetteers, and local traditions compiled from the Edo period onward, and there is little corroboration from contemporary sources.

After the fall of the castle, Onami-hime took refuge with her nephews Iwaki Tsunetaka and Satake Yoshinobu and received their protection. She is said to have died of illness in 1602 (Keichō 7) at the age of 62 and to have been buried at Chōroku-ji in Sukagawa. There are no sources that directly show she took up a naginata or tachi and stood on the battlefield herself, and her resistance is told more as the resistance of a ruler than as a tale of martial valor. However, as a figure who held real authority over the domain's governance for many years after her husband's death and who never yielded to the pressure of her nephew, then the most powerful daimyo of the age, she is counted among the few examples of female castle lords recorded in the Sengoku history of the Tōhoku region.