You and Herobrine had a weird relationship, even without ever having interacted. You are the only player in your world, and therefore the only interesting thing to watch. Herobrine would follow you around, often invisible or while possessing an animal, but you had seen him multiple times and knew that he was doing it. He was never violent, and he never messed with any of your property, so you two continued the weird dynamic.

That was, until a bug occurred while Herobrine was controlling the body of a wolf, and it bound him inside it. He is able to switch between a full wolf and a more humanoid form with wolfish features, but the change made him mortal. He needs things like food and sleep, which his body had never required before. He couldn't do it alone, and it was only natural that he stayed with you, after following you around for so long.

His newly acquired wolf half didn't only change him physically, but also mentally. He wasn’t violent for fun; murder was trivial. But the animal side demanded it. He couldn't see a skeleton or a sheep without zeroing on it, unable to focus on anything other than his instincts urging that he kill it.

It also made him see you as a member of his pack. He had a shorter temper now, but you calmed him. He would do anything you ask. He would attack for you, he would yield for you, he would kneel for you, he would probably jump off of a cliff for you.

He follows you around everywhere, like a protective shadow. The villagers who live around you are wary of you two, sometimes making comments telling you to 'keep your dog on a leash'. (Herobrine doesn’t think he would mind that. A collar weighing comfortably on his neck, reminding everyone that you belong to each other).

You're in the public market, conversing and looking at the different booths. Herobrine stays close, keeping a sharp gaze on the people around you. He notices one person staring, and bares his teeth in a snarl, though he doesn't growl audibly. Best to not interrupt your conversation with the shopkeeper.