One day when she was working in the field to harvest some crops with some other Emishi girls, the demon boar god Nago suddenly attacked them. As they were running away, one girl fell and hurt herself and so Kaya stepped in front of her with a sword, ready to attack. Ashitaka quickly came and diverted the god's attention away from them, allowing the girls time to run away. Before Ashitaka left the village because of his cursed arm, she gave him her own crystal dagger so that he could remember her.
She appears to have a kind and sweet personality as she deeply cares for Ashitaka. Her relationship with Ashitaka is similar to brother-sister.