Luhan is, what we know as, Cupid. 

He spends his days and nights wandering, matching up compatability levels.

That's when he finds Baekhyun and Chanyeol. 

Two people who couldn't hate each other anymore if they tried.

But they were perfect for each other.

And Luhan knew it.

This was the most important project he'd ever gone forward with.

Once you start a project, you can't turn back.

Or you're cut off.

Your job.

Your wings.

Your life.

Gone.

If Cupid can't make two people fall in love, he has no purpose.