After graduating from Nagano Normal School, she worked for two years as a teacher, during which time she met the poet Mizuho Ōta, and began to compose tanka verses herself.

She entered the Tokyo Women's Higher Normal School (present-day Ochanomizu University) in 1906 and married Mizuho Ōta when she graduated.

While teaching at a girls school in Tokyo, she assisted her husband in his literary magazine, Chōon, by contributing tanka verses and helping in its overall administration.

She published numerous anthologies of her poetry during her lifetime, including Fuji no Mi ("Wisteria Beans"), Asa Tsuki ("Morning Moon"), Asa Ginu ("Linen Silk"), and Kamakura Zakki ("Kamakura Miscellany").

Mitsuko and her husband Mizuho Ota began to live in Kamakura, Kanagawa Prefecture from 1934, calling their retreat "Yo-yo Sanso."