Who is Karl-Heinz Kornfield from The New Confessions and what is their importance?

Karl-Heinz Kornfield is the young soldier, who is assigned to guard John when he is taken prisoner of war during World War I. Kornfield is gay and trades food and later a book to John in return for a kiss. He meets up with John on several occasions after the war, and they work together on the first segment of "Confessions."