Eldest daughter of Takeda Shingen and Sanjou-no-Kata. She married Houjou Ujimasa, heir to the Sagami Houjou Clan, on the occasion of the three-way alliance between the Takeda, Imagawa, and Houjou clans in December of 1554 when she was 12 years old. The wedding was a glorious affair and had 10,000 people in the procession. She gave Ujimasa a daughter and five sons, including his heir Houjou Ujinao in 1562, and their marriage was thought to be a happy one.

However, when Shingen attacked Suruga in December of 1568, breaking the alliance, Ujiyasu flew into a rage and had the marriage between Oubaiin and his son broken off. Oubaiin was sent back to Kai, where she later entered the priesthood at Daisen Temple in Koufu. She died at the age of 27.

Shingen built a sub-temple (part of his family temple) in her honor, as did Ujimasa when the Houjou and Takeda formed another alliance in 1571.