This seems to be the only thing I can write at the moment, which makes me grumpy, but better this than nothing. Sorry that it's not quite as Happy as you probably intended when you asked, sna32.
He takes seven assassination missions one after another in the course of a month, and he barely has any downtime. That month is a September. Kakashi is newly sixteen, and he is beginning to forget the difference between living and dead. When he wears his ANBU mask, it is hard, and colder than the flesh of his victims. Maybe he's more dead than they are.
In October, he returns from the last of these missions and finds that somebody is already in his cramped apartment. He nearly attacks the dim figure, but something deeper than any single sense of his identifies her in a split-second. It's Rin.
She's been busy. He didn't get a chance to see her last month, and a small, frightened part of him hoped he never did again, because he doesn't want her to see what he's become. But most of him--nearly all of him--was afraid of her absence.
Now she takes his hands in hers, which are very warm, and puts them on her waist. She reaches up, touches his face, pulls down his mask, and reminds him that he is alive.