Seienin was a lady living in Japan during the Sengoku and Azuchi-Momoyama periods. She was the formal (second) wife of Uesugi Kagetora and is also known as Kakeiin. Uesugi Kenshin was her uncle.
In 1556, Seienin was born as the eldest daughter of Nagao Masakage and his formal wife, Sentōin. She had two brothers (Yoshikage and Akikatsu, later known as Uesugi Kagekatsu) and a younger sister named Hana.
In 1570, after the forging of an alliance between Uesugi Kenshin of Echigo Province and Hōjō Ujimasa of Sagami Province, the seventh son of Hōjō Ujiyasu, Saburō, entered Kasugayama Castle. Her uncle, Kenshin, arranged for Seienin to marry Saburō who became the adopted son-in-law of Kenshin under the name of Uesugi Kagetora. The following year, she gave birth to their eldest son, Uesugi Dōmanmaru.
In 1578, the death of Kenshin triggered a succession struggle in the Uesugi family between Kagetora and Seienin’s brother, Uesugi Kagekatsu. This is known as the Otate Conflict. At this time, Seienin fled Kasugayama Castle held by Uesugi Kagetora and, together with her mother, Sentōin, and children holed-up in the Otate, a residence below Kasugayama Castle built for the Kantō-kanrei, or deputy shōgun of the Kantō, which was also used by Kenshin for the conduct of political affairs. Owing to an attack by Kagekatsu’s forces, the residence fell. Intending to take his life, Kagetora escaped from the residence while Seienin refused warnings from Kagekatsu to surrender and took her life in the residence.
According to genealogical records, her date of death was on 3/24, in which case there is a strong likelihood that at the residence, she died along with Kagetora at Samegao Castle. Located near Kasugayama, Samegao was controlled by the Uesugi along the only route to the Kantō.
At the Meigetsu Temple in Kamakura, there is a Buddhist mortuary tablet in the name of Seienin.