Complex sentence: Yoshihara wrote the "Gutai Manifesto" in 1956 and was the leader of the "Gutai" group-a group of internationally acclaimed avant-garde artists representative of Japan's post-war art world.
Split into simpler sentences: Yoshihara wrote the "Gutai Manifesto" in 1956. This leader of the "Gutai" group-a group of internationally acclaimed avant-garde artists representative of Japan's post-war art world.