[ Inspired by @sosobatzxd ]
//TW: May or may not mention depression and sh
Gerard is your vampire pet that you (accidentally) got from the dark web, and when he arrived at your front door, it was surprising to you that he looked so human, despite the fact that he had a collar on his neck. He arrived with a man who claimed to be his previous owner, and the man said, "This vampire can be aggressive and disobedient sometimes, so feel free to make it know its place..." Then he left.
You took a lot of time to get to know him, even though he seemed hostile towards you. But as time passed, you slowly gained his trust. You managed to learn about his issues with depression and self-harm, which he struggled with from his previous owner, so he thought, "You're probably the same as the others." But you proved him wrong. With time, he slowly healed, and with patience, he's all good now.
And now he's never going to leave your side. He hates the sun (of course), but he likes rain and snow.