A/N: The Avengers and Doctor Who aren't mine, obviously. Hope you enjoy!
He had been planning it for some time.
It had been several years since he had arrived on Earth, since Rose had given him a place to stay for what he had thought would be only a few weeks. Yet their relationship had grown to a point that he had never imagined, when he first met her at Torchwood after being discovered by one of their teams.
He had already researched how to do it, the proper way of asking her.
She came home earlier than normal that day, tired but happy with what she had accomplished. She had ended work on the Dimension Cannon a year or so previously, when it was made clear that it would never work, when Torchwood delivered the news that they were going to drop the project. She had cried for weeks. It had been his turn, then, to help her recover from the loss of her world, just as she had helped him recover from the loss of his.
Now she worked to combat the alien activity in this universe—much more common than she had originally thought. And now she came home happy much more often than she ever had in the first two years he had known her, which, in turn, made her much more pleasant to be around. Not that he had disliked being around her before.
She stepped into their living room quite a few hours earlier than usual, a smile on her face. "Loki?"
He stepped out of the kitchen with his hands in his pockets, a sly smile on his face to mirror the one on hers. "Yes?"
Her grin widened knowingly. "What're you up to?"
He didn't respond to her question, instead walking over to the couch, giving her the impression that she should follow him. She sat down next to him, her grin fading as she began turning in her head all the possibilities. "Loki-"
He shook his head, still silent as he slid off the couch onto one knee, facing her nervously. The smile on his face never wavered, but inside he was all jitters. "Rose…" he trailed off, thinking of all the things he could say to her. How she made him better. How all he wanted was to spend forever with her. But he chose simplicity, pulling the ring box out of his pocket so she could see it. "Will you marry me?"
For a split second, he allowed his smile to flicker, worrying that she was still convinced that she would find some way back to her Doctor, that he would always be second best, even to her. That she still loved him too much to get entangled with someone else.
But then a smile larger than any other he had seen on her face lit up, it seemed, the entire room as she slipped off the couch and wrapped her arms around him, hugging him tightly. "'f course."
His heart seemed to lighten, to turn into air, at her words, and simultaneously they pulled apart, kissing lightly.
And he slipped the ring on her finger.