Who is Pilar's Friend from By the River Piedra I Sat Down and Wept and what is their importance?

Though the reader never learns his real name, Pilar's friend is a man with whom she grew up. They were children together in Soria, and he was in love with her from the time they were young. He told himself that he would tell her he loved her; when he went to seek a pendant she had lost, he mustered up the courage to tell her, only to lose that courage when he saw her again. He never gave her the pendant back, and vowed he would return it only when he could find the courage to tell her how he felt. He leaves Soria to travel the world and secretly enters seminary. He often writes to Pilar about his travels but never tells her he is a seminarian.