When you think about it Crowley and Aziraphale must have experienced all of those ancient rituals of kinship and affection throughout History. Like. When people kissed and held one another without a second thought. When it was overall easier to express affection between family, friends, or lovers, regardless of gender, to the point that they must be pretty confused--and disheartened--by modern days' general prudishness
Like. Imagine them in 5th century BCE Persia, where men kissing each other on the mouth was a sign of respect, of being equal to one another ; imagine them wordlessly kissing for the first time like that, instead of their usual colder, disrespectful kiss on the cheek ; because they've accepted that they're not enemies anymore, that they're the same in many ways, but they can't articulate that openly, so they seal the knowledge of their growing respect and affection with a kiss of equals
Imagine them in ancient Rome, where kissing was like shaking hands, only with a million little rules and customs ; imagine them practicing the osculum (close-mouthed platonic kiss between acquaintances and friends) for the longest time, until crowley says something infinitely sweet and impossibly good one night after one too many cups of wine, and in his surprised happiness, aziraphale grabs him by the ears and gives him a basium (open-mouthed kiss of strong affection on the lips, sometimes erotic), making crowley promptly fall over his bench and into the Tiber ; they keep saluting one another with a basium from then on, along with affectionate then-platonic kisses on closed eyelids, brows, necks- up until the practice falls out of fashion along with the empire
Imagine them exchanging kisses of peace when the first Christians start greeting one another with them, as the apostles once did ; Crowley vehemently refusing to call them 'holy kisses' in case his mouth spontaneously melts whenever it meets the angel's, and Aziraphale always indulging him, laughing on his lips while they chastely kiss hello and goodbye
Imagine them during the middle ages, when kisses are not so freely-given anymore, having become so much more important in their symbolism ; crowley kissing aziraphale's hand like a vassal or knight does his lord or lady, reverently, fervently, chastely, with all the wordless loyalty he already feels for him, refusing to admit that all the romance of courtly love has gone to his head but being perfectly aware of it nonetheless ; and it's with a kiss on the lips that contracts are signed at this point of History, and so that's how they seal their Arrangement, finally reaching for each other as one for a long-missed embrace that feels too much like a reunion after the sobering Crusades
Imagine them post-renaissance, during the georgian/regency Era even, in Europe where affection and love between men have become heavily guarded and codified : when they feel their bond and affection the most ardently after millenia of learning to know and love each other, but unable to express any of it ; when suspicions of homosexual love is punishable by death in England, so they have to act distant and stiff and pretend they don't remember what it felt like to sit in each other's laps in Persian courts or taste wine through the other's lips during Bacchus feasts. There are hidden places where they could meet, Molly houses and ungentlemanly balls and back gardens, but somehow it seems like the English ways got to Aziraphale, because it doesn't seem proper anymore to say 'please, I'm begging you, come to a place of ill-repute and risk discorporation with me, because in these desperate times, I'm terrified I'll forget how good it felt to kiss you'. Instead, he doesn't say anything, and hides himself in secret clubs, silently waiting for crowley to stop likewise hiding in his century-long sleep.
Imagine them during a summer of love, catching a glimpse of the other among thousands of bodies dancing and singing, being driven together like orbiting moons until they crash into one another, embracing and laughing and yes, kissing in relief, two mouths who have been parted for far too many centuries, holding each other, rocking into each other's arms while the music plays on, aziraphale laughing against crowley's beatifically smiling lips that he never knew how much he had missed the Adamites before this moment ; the both of them not knowing of the riots coming soon in Stonewall, but wordlessly, desperately hoping, hoping, hoping.
Imagine them now, a lifetime later, finally learning all over again what the other feels like, now free to express the love they've been feeling for ever, with kisses, with touches, with words ; not just because humanity is finally starting to get over itself, but because heaven and hell are as well ; there are no more self-imposed inane rules, no more weight on their shoulders, and they know they can't--won't be judged ; neither on this plane nor the next. And they can learn how to kiss, like it's that first time in Persia, all over again.
