The female protagonist of the series. She is described as a calm, collected, and very observant. She is 10 at the beginning, then she becomes 14 in the first time-skip, and 18 in the second. Due to the influences of her mother Soyon and foster father, John, Erin carries a unique perspective in caring for beasts. Many people think that she is too curious, which simply gets her in trouble. Erin is truly caring towards people and animals, even to the point of worrying more about others than herself.

Because Erin's mother was of the Mist People, she inherited her green hair and eyes. Some people first believed that she was able to be close to Lilan and Eku because she learned magic tricks of the Mist People from her mother, but they later see her as someone who just want to truly understand animals.