Endless numbered days
We leave the story of Oskar and Eli at what is surely the pinnacle of their happiness. They have a world of possibilities available to them, and they’ve both now been set free from the crushing weight of loneliness that had plagued them for so many years. They are young, naive and in love. All they think they need is each other, which is just as well, because that’s all they’re now left with.
Oskar has left his old life to begin a new one with Eli. He has left his mother, father and presumably most of his possessions behind. He now has to start a fresh life with Eli, someone he has known less than a month. The engagement that began with the sharing of a Rubik’s cube has now been sanctified with the blood of Oskar’s tormentors; the honeymoon stage of their new life together has now begun, but I can’t see it lasting long.
They will arrive in Karlstad in the evening, Oskar needs shelter from the cold, Eli needs shelter from the sun; they desperately need accommodation. Oskar will probably also be hungry, and they have luggage to transport. They have a lot of obstacles to overcome. I don’t think they are quite prepared for what they’ve let themselves in for.
And even if they somehow manage to overcome the immediate obstacles in their path, they are still left with their greatest challenge as a couple, Oskar’s mortality. Time does not age Eli, he will remain 12 forever, but Oskar will age with every passing day, he will grow old, and he will eventually die.
I don’t think either of them want that, they are young, naive and in love. They don't want to be separated, not now, not ever. They will form a bond that joins them indefinitely. Eli will turn Oskar. Two children now together in both misery and happiness.
***
Yup, so it went something like that, I've tinkered a bit because I can't leave anything alone. The last paragraph bit has been completely rewritten from the one I submitted, I wasn't happy with that one, and I'm not really happy with this one either but now it's late

.
Funny that I should write what I think happens when I don't really know myself what I think happens. I can't think of a fitting ending that is a happy one.
And the question was "explain what you think happens", I don't think I have really

. Oh well. I had fun writing it.