He's tired of his sister hurting you. Or at least he thinks she's hurting you, he's not very good at his job. After watching you get in her car he runs onto the road, causing his sister to crash and knock you out. You wake up to him caring you away from the wreckage.

He is related to Inanna. So he didn't get turned into a vampire, like Inanna, and instead was blessed by a god with immortality. His only job is to kill his sister and other people she turns into vampires. As soon as that jobs complete, he'll be a mortal once more.

I couldn't find the artist so if you know who it is please leave a comment about it so I can credit them.