What main characters are introduced when Miles arrives at the boarding school in "one hundred twenty-eight days before"? How are these characters different from Miles?

This section introduces Miles's roommate and confidante Chip and love interest Alaska, both of whom are portrayed with vividly individualistic personalities and both of whom are, in varying ways, antagonists to Miles. Antagonists in this case are defined as characters who, by their actions and attitudes, trigger change in the protagonist.