Aiden thought quickly about his reasons for believing he was a Witch. He remembered Rainbow, the bird who was currently his spirit animal. And the fact that only Witches could connect with a spirit animal, and Rainbow himself had told him this and that it's even more impossible for another race to connect with a spirit animal since they don't understand nature. So, how could he possibly be a wolf if he had his own spirit animal? He was clearly a Witch.
However, he immediately remembered the promise he'd made to Rainbow, a promise that he wouldn't tell anyone about the bird being his spirit animal, as the world must not know that spirit animals still existed. It wasn't that he didn't trust Julian and Ashton to keep a secret, but Aiden truly believed that the only way to keep a secret was to keep it to oneself.
A secret told to a second or third party was a secret no longer.
