Complex sentence: In company with Toshiro Mifune, Shimura is the actor most closely associated with Akira Kurosawa and he appeared in 21 of Kurosawa's 30 films.
Split into simpler sentences: In company with Toshiro Mifune, Shimura is the actor who is most closely associated with Akira Kurosawa. Shimura appeared in 21 of Kurosawa's 30 films.