Matsuzaka played the "Madonna" role in the 1981 film Naniwa no Koi no Torajirō, the 27th in the Otoko wa Tsurai yo series.
Keiko also appeared in Legend of the Eight Samurai (1983), Shin Izakaya Yūrei (1996), Dr. Akagi by Shōhei Imamura (1998), Runin: Banished by Eiji Okuda (2004), and Inugamike no Ichizoku (scheduled for release in 2007).
The 1975 Taiga drama Genroku Taiheiki featured Keiko as Aguri (Yōzen'in), the wife and later widow of Asano Naganori in the dramatization of the events of the Forty-seven Ronin.
She then appeared in Kusa Moeru in the same time slot in 1979, and portrayed Sada (Kawakami Sadayakko), the lead role in the 1985 Taiga drama Haru no Hatō.
Having portrayed Aguri, Keiko also played Riku, the wife of Oishi Yoshio, in Chūshingura Yōzen'in no Inbō, broadcast on January 2, 2007.