She spent her childhood in Fukui city, where her wealthy family ran the geisha ryokan Beniya at Awara Onsen.

Later her father was defeated in the general election, and, heavily in debt, the Yamatani family left Fukui for Tokyo.

In 1989 Yamatani ran for a seat in the House of Councillors as a Democratic Socialist Party candidate, but was defeated.

In June 2000, she was elected to the Diet of Japan on the Democratic Party ticket as a proportional representative.

Affiliated to the openly revisionist organization Nippon Kaigi,[3] she is also a supporter of Japan's territorial claims and has called for special legislation to restrict land sales to foreigners on Tsushima Island and to implement measures to boost its local economy without having to depend heavily on South Korean tourists.