From 1955 to 1957 he studied drama at the Max-Reinhardt-Schule, today known as the Ernst Busch Academy of Dramatic Arts.
In 1964, Karsunke moved to Munich, where he became involved with the Außerparlamentarische Opposition, becoming a spokesman for the Campaign for Nuclear Disarmament in 1968.
Along with other leftist authors, he founded the literary review Kürbiskern, for which he served as editor in chief from 1965 until August 1968, when he resigned as a protest against the Soviet repression of the Prague Spring.
[citation needed] In the early 1970s, Karsunke befriended Rainer Werner Fassbinder, appearing in his films Love Is Colder Than Death (1969), Gods of the Plague (1970), and Berlin Alexanderplatz (1980).
From 1976 to 1979 he served as Fassbinder's technical adviser at the German Film and Television Academy Berlin.