See how often they participate in the script: HERE.
Character Story: The owner of a boat rental shop upstrea from Lake Hylia. When Zora's Domain, the source of the lake's water, freezes, business comes to a standstill.
Race Story: Humans typically live peacefully with other races throughout all of Hyrule. The more specific Hylian race is a subcategory of humans. They can be differentiated by their ears -- Humans have rounded ears and Hylians have pointed ears.