It's as if they've always known. Ron and Hermione, immediately following the battle.
Hermione can feel it as she flings her arms around him; he trembles all over, and she knows it's from laughter and tears and fatigue and shock and just everything that can make a person shiver like he is, but right now all she cares about is the heart beating beneath his ribcage and the solidity of his warm, living body -
- and the feeling of Ron's hand slipping around her own like it's completely normal, like they've been doing it all along. She looks at him; he stares back with the intensity of a man who has seen so much that it is all he can do now to keep looking.
They're shoved away from Harry by the surging crowd (Hermione just catches a glimpse of Ginny crashing into his arms) but it doesn't seem to be a problem, because in the end and through it all and after it's over, Ron and Hermione are still wound tightly together, and she kind of wants to cry from the total relief she is feeling - they've done it. They've survived.
As though he's heard her thoughts, Ron pulls her closer and buries his face in her hair despite how horribly tangled and full of dirt and blood it is; and maybe she's not supposed to hear it, but he whispers, "I love you," and it makes her chest constrict in the most wonderfulamazingfantastic way.
So, even though there's time for waiting now, Hermione doesn't. She stretches on tiptoe, winds her hands around the back of his neck - ignoring the scrape she feels there - and kisses him. And it's different this time. There is no good-bye or I wish I wish I wish or we need more time or could've-would've-should've, no desperation. There is only hello and I'm sorry I'm late and I am alive and never never leave me and don't let go.
Before she drops back off her toes, Hermione says, "I love you, too."
Again, he just looks at her, eyes darting all around her face like he wants to remember this moment forever -
Then he's kissing her again and nobody is there and nobody has died and nobody matters but the two of them, only the two of them.
It's as if they've always known.