Who is Pumpkin from Lost Names: Scenes from a Korean Boyhood and what is their importance?

Pumpkin is the name of the bigger boy that follows the boy and his mother to school the first day. Pumpkin is the class "cut-up" by making "oink" sounds but later helps the boy when he defends himself against the Japanese teacher and tells him he should be class leader. Pumpkin leads a group of fourteen boys that come to congratulate and wish him well when he recuperates. Later that day Pumpkin drowns when he dove into the river and was found dead downstream. He is one of two characters that are identified by name rather than nationality, title or role.