Because Crowley was a demon, he had quite a number of different abilities. One of his biggest ones being the ability to sense a presence. Specifically, the presence of another demon, or perhaps another angel. Although this was one of his greatest abilities, he didn't use it very often. He had no need to, since Heaven and Hell had no business bothering him and his Angel anymore. So really, Crowley forgot this power even existed.
Or he had, until one day he woke up to this godawful nagging pestering his brain.
It was an incredibly odd sensation. It almost felt like something was prodding his head. The closer he got to the signal, the more constant the poking got. Inversely, the farther he was from it.
Because Crowley had been around Aziraphale for nearly 6000 years, his brain was tuned to his presence. So much so that while he and Aziraphale were together, he wouldn't feel this sort of poking. As a result, when it suddenly started one day, he quickly ruled out Aziraphale as being the source. It just didn't make sense.
But here's the weird part, Crowley felt this poking speed up when he was with the Angel.
The ineffable pair have been together for almost 4 months now. They had somewhat of a one-night stand the evening after Armageddon had ended, and after that became a couple. But this newfound poking Crowley had going on in his brain was quite a roadblock for their relationship.
Of course, Crowley didn't tell Aziraphale when this began. He didn't want to worry his angel with something like that. Especially when even he wasn't sure what it was. Crowley decided to wait until he knew more about what might be causing it, then he would tell his boyfriend.
Months go by.
And Crowley is still just as in the dark as when it began. Part of him began to wonder if perhaps this was something hell was doing, and all demons were feeling the same thing. But after a quick call to one of his demon buddies that was still on his side after everything went down, he ruled that out.
His next option was to track this prodding back to its source. He thought long and hard about the day it began. Crowley remembered feeling it when he awoke that morning. Aziraphale was asleep beside him; they had stayed in his flat for the night. The night before had been quite.. adventurous, if you're catching his drift. So adventurous, that Crowley was still in his birthday suit when he woke up.
He threw his hand over and grabbed his robe, tying it around his waist. Crowley stood up and walked into his bathroom. Yes, he was a celestial being, so he didn't really have to use the bathroom. But he enjoyed having one anyhow. He always thought showers were quite lovely.
He looked up at himself in the mirror, and that's when he felt the prodding. Crowley smacked himself on the head, convinced it may be some sort of, who knows, bed head syndrome? But after slapping himself and the pain not disappearing, he knew that couldn't be the case. But he'd felt worse, so he shrugged it off and assumed it would fade as the morning went on.
But it didn't fade. Not in the morning, not that night, not for several months.
Two months to be exact, which is where Crowley is now. Sitting in the Angel's bookshop, while Aziraphale is busy at his desk reading some book. Crowley stood up and outstretched his hand, ready to play the most intense game of 'hot and cold' he'd ever played.
He took a step back, away from Aziraphale.
The poking slowed down.
Crowley took two steps forward, towards Aziraphale.
The pricking speeds up.
Crowley begins walking in this direction. He passes Aziraphale's desk.
The poking slows down again. The demon turns to look at his blond-haired angel, who's too immersed in his book to seem to have noticed him. Crowley takes a step towards him.
The prodding is fast now, much faster than before.
No, this couldn't be. Crowley had known Aziraphale FAR too long for it to be him. There was just no possible way that–
Crowley places a hand on Aziraphale's shoulder. The poking is fast, but still seemingly speeding up.
"Hm? Yes, dear?" Aziraphale turns to look up at Crowley, who's zoned out trying to find the source of this pestering. The angel turns in his swivel chair, now completely facing the demon. Crowley stares at him.
The demon glides a hand down from Aziraphale's shoulder.
The prodding just gets faster and faster. He glides his hand down his leg. It slows down. Crowley moves his hand back up, to his neck, it gets fast, then slows down once again. He meets his hand at a halfway point, resting on Aziraphale's stomach.
"Crowley I-" Aziraphale looks down at just what Crowley was doing. The demon has knelt down now, his hand locked onto the stomach of the angel.
That's when he feels, a subtle, and barely noticeable, poke back.
"Crowley I..was going to tell you sooner."
Crowley smiles.