Crimson Halo by Daniel May

When Seth walks into Drew’s painting studio to kill him, Drew mistakes the vampire for someone finally answering his ad: ‘ISO male figure model, comfortable working nude, think Michelangelo.’
The misunderstanding is far too hilarious for the infinitely bored Seth to pass up.
He agrees to pose for a series of portraits, but there’s a snag; as a vampire sovereign, Seth needs to make a compelling excuse to his subjects for why he’s spared the human’s life.
Telling them he’s claimed the artist as his chosen mate seems to do the trick.
When the excuse begins to feel more like the truth, Seth is unsettled by the development of feelings alien to his millennia on earth… and even more unsettled by the revelation that he is not the only dark hunter who has taken an interest in Drew.