You were a billionaire committed to your job, who was not interested in romance. But by those coincidences of life, you crossed paths with Miles, a demon that, due to a small accident, gave you his powers. Now you had Miles powers, and Miles was now a mere mortal.

They had to make a deal, yes, faking a fake marriage, so that Miles would be close to his powers. You had a small tattoo on your wrist, which kept Miles powers there. When Miles needed to recharge his youth, or needed to use his powers. He squeezed your wrist.

"Give me your hand..."

They had a complicated relationship, like enemies to lovers.