Honorific terms

Basically there are two kinds of honorifics and respectful or humble term (or three kinds of honorifics when you also count formal term as one). Respectful terms are used when a speaker with lower position speaks about a person with higher position and humble terms are used when a person with lower position speaks to a person with a higher position.
Then how to describe a situation that a person with higher position and a person with lower position talk each other? Then, humble terms are used. It means that when a person with high position's behavior is described in humble terms when he or she speaks with lower people or person.
This was the most difficult point that I found in the entrance exam of Kansai University after I took it. When I read the Japanese classic literature writen in Kamakura era in the test afterwards spending tremendous time, I came to realize what complexicated me. We should put subject at the biggining of every sentence we make in Japanese as they do in western languages.