Levi has grown up with Zim. The two are like brothers, and they act accordingly. Zim tells Levi what he thinks and feels, something that only true friends can do.
Pearl is open and honest, but she also often responds to Levi with the things she believes he wants to hear. Pearl is a Chinese Jew being educated in a Catholic school. In terms of Levi's concern for his brother, Boaz, Pearl is more understanding than Zim, but she doesn't provide a lot of support.
In the end, both of his friends accompany him to find his brother. No matter their differences, friends come in all shapes and sizes, from all walks in life, and from numerous backgrounds. Sometimes differences allow friends to pull closer together..... their perspectives, though differing, serve to shed a different light on events and occurences.