they don't start "dating" so much as they just. fall into a relationship and all of a sudden they're holding hands and spending a lot of time together and kiSSING(!?) and neither of them really knows when it started but they don't care. james says i love you to everyone bc he's v affectionate but when he says i love you to lily it's Different and everyone can hear it it's not i love you it's I Love You every time no matter how small the scenario it's always I Love You
James is pretty sure he’s been in love with Lily Evans since the beginning of fifth year but then he realises that’s not love because you can’t love someone you don’t know. She’s just very very very attractive. Then the Incident happens and he doesn’t know how he feels and Lily is even more in the dark because they were friends except for when he was a cock but now all she feels when she looks at him is burning burning burning.
The summer cools her off and she doesn’t expect him when she gets back. Well, she does, she just doesn’t expect so much of him. He’s grown, again, and she’s not sure if he’ll ever stop, and it suits him. There’s less tripping and squeezing under desks. Finally, he seems able to actually control all of his limbs. He can’t control his eyes though. James finds them wandering to her during lessons, lunch, once even a quidditch match. She’s so easy to spot with wine red hair and eyes which don’t seem to want to meet his, but do anyway. She keeps noticing things about him, things that weren’t there before. Or maybe she just never let herself notice them before? It happens all the time and she hates that she loves it.
It’s easy. Being friends. Like picking up a book your mum used to read to you at bedtime. You think you’ve forgotten the words, but they all come flooding back. That’s how it feels. To have his arm over her shoulders, to duel with him in DADA, to steal toast from his plate, to save the strawberry botts for her, to watch him and only him on the pitch, to share Potions notes, to throw parchment notes at each other in History of Magic, to borrow his scarf, to hold her hand to help her across boggy Scottish soil. All of it, everything - it’s natural.
People start assuming they’re together. They stop being Lily Evans and James Potter and become Lily and James, addressed as one. Sirius rolls his eyes and becomes bitter, interrupting conversations and not moving to allow Lily a seat. Mary and Marlene giggle and wink at her whenever she sits besides him, the traitorous gits. Everyone knows something is up. Except for them.
Then it’s summer again and he’s so far away and she’s too far away and they write. They write too much to go unnoticed, by friends and then by parents. Mrs Evans try to be nonchalant as she asks who all these owls are from. Mr Potter ruffles James’ hair when Sirius points out that James is spending more time replying to letters then he is playing quidditch. There’s talk of meeting up, but it never happens. Lily never quite manages to draw up the courage to tell James which bus route to take. James always fails to write down where the spot for apparating to is. So they go all summer never seeing each other, except in familiar g’s and friendly scribbles which Lily has to spend ages deciphering into something legible.
September comes and they’re both wearing their badges and neither one is surprised but both are slightly hurt the other didn’t mention it. Excuses are useless so they just say well done and attempt to organise the prefects, even though Remus spends the whole meeting making suggestive gestures at one of them when the other isn’t looking. And nothing has changed. Except James is taller, again, and Lily’s hair is shorter and her boobs are bigger (but James definitely hasn’t noticed that), but they’re the same. No one blinks twice when they’re the only two left in the common room. Everyone is used to seeing them together, heads bent close, people uncertain if they’re discussing rotas or the latest transfiguration journal. It becomes customary that if Lily’s the only one on a sofa, the other half is reserved for James. If James falls asleep with her head in her lap, there’s nothing unusual about it.
People call them a couple and they don’t think to correct them, not having discussed it but sort of knowing anyway. She kisses him goodbye outside the Three Broomsticks once, a peck on the cheek, the Marauders going onto Zonko’s and the girls visiting Honeydukes. He blushes but she doesn’t and then that’s a thing too. It doesn’t take long before the kisses are on the forehead, the nose, the lips. Always gentle, quick and not really anything of note except, every time lips brush skin, their hearts race faster. So no one’s surprised when, with the excuse of mistle toe, a short and swift kiss becomes a long, soft and languid one. (Until Peter throws a cushion at them.)
They’re dating, going out, boyfriend and girlfriend. They’re every synonym for together and they’re happy. Every inch of them says ‘I love you’, but they never say it. And then they do. And it just happens, and their hearts beat faster, and their breath comes short, but they’re not surprised. They know, everyone knows, how could they not be in love? James says it first, casually and then not casually at all. Lily says it back, into his neck, his lips, his heart, both of them smiling like they’ve been given the sun on a string.
So they’re in love and it’s a shred of light in a world which keeps getting extinguished around them. They’re not sure how or when it happened but it did and when they have nothing they have each other, because that’s just how it is.