Seienin was the daughter of Nagao Masakage and niece of Uesugi Kenshin, who arranged her marriage to Houjou Saburou (Uesugi Kagetora) when he was adopted into the clan in 1570. She was also older sister to Nagao Akikage (later Uesugi Kagekatsu).

Seienin gave birth to Doumanmaru the year after her marriage.

In the Otate no Ran that arose after Kenshin's death, she followed Kagetora to the Otate. Some records indicate that she may have committed suicide at the Otate when Kagekatsu refused Kagetora surrender; it's more likely, however, that she died at Samegao Castle with Kagetora.