It's a god or a devil in one thought.
He was sneaked into the demon world by mistake, and then released a real demon out of ignorance.
It's a sin, it's fate.
Destined by fate, they will repeat the same mistakes as they did thousands of years ago. Whether they meet or miss each other in the end.
What is the truth, what is love and hatred, what is life and death...
Whether they can escape the tricks of heaven and when they can achieve enlightenment.
Angels, demons, good and evil, yin, yin and yang, lingering...