Who is Tsukada from Deep River and what is their importance?

Tsukada is a wartime buddy of Kiguchi. He stays with Kiguchi in the jungles of Burma when Kiguchi falls sick with malaria. Tsukada eats the flesh of a dead soldier to stay alive so that he can save Kiguchi. After the war, he is overcome with guilt, and he drinks himself to death. As he is dying, he wants to know if God can forgive him for what he's done.