Born in 1547 in Owari Province, the daughter of Shinohara Kazukazu. Raised in the Maeda household, she married Maeda Toshiie at age 12 and bore him 2 sons and 9 daughters over about 21 years. She supported Toshiie's rise through her household management and maintained a close friendship with Nene, Toyotomi Hideyoshi's wife. When Toshiie died in 1599, Tokugawa Ieyasu pressured the Maeda clan with accusations of treason. While heir Toshinaga advocated armed resistance, Matsu volunteered to go to Edo as a hostage to preserve the domain—a decision that secured Kaga's million-koku territory. She spent 14 years as a hostage in Edo before finally returning to Kanazawa in 1614. Taking the religious name Hoshun-in, she died in 1617 at age 71. She became widely known through the 2002 NHK Taiga Drama 'Toshiie to Matsu.'

Intelligent and decisive, the model of a wise wife and good mother who supported Toshiie. Her resolve to become a hostage showed courage surpassing many warriors. Skilled at mediating within the household, she contributed greatly to the Maeda clan's prosperity.

Her decision to volunteer as a hostage to save Kaga's million-koku domain is celebrated as one of the most remarkable acts by a Sengoku-era woman. Her behind-the-scenes support in building the Maeda household's foundations is highly regarded. The 2002 NHK Taiga Drama 'Toshiie to Matsu' brought her nationwide fame.