Who's story?

This first chapter of The Sun Also Rises begins describing the life of Robert Cohn who is an American living in Paris. However, this story is told in the First Person point of view. Because of this, I am thinking that this story will focus mainly around two characters who are friends. The character telling the story is named Jake Barnes, and he is the friend of Cohn. However, I am not certain that they are too great of friends becuase Jake only describes themselves as tennis friends. This gives the impression that while Jake is fond of Robert Cohn, he does no sincerely want to be his best friend. This can be found at the end of the second paragraph on page 13 when Jake describes Robert's two friends. Based on reading the summary of the book, I am thinking that the story will focus on their travels together through Europe. However, this chapter does not talk much about any other third parties other than Frances who is Cohn's wife who wants to marry Cohn.