The Doctor has a habit for swearing in Gallifreyan. Rose has noticed this, after all its the only language the Tardis doesn’t translate. And he only ever uses it when he’s shouting in frustration during Tardis repairs when the Tardis shocks him or - very rarely - when they’re running for their lives she hears him mumble it under his breath.
Then he regenerates.
Many things change after that. But the swearing continues. Although it’s different. More words have been added, new words, different words. It’s not just the occasional word shouted out of habit, it can be a whole rambled conversation. Rose doesn’t question it. Even though it doesn’t occur when the Tardis shocks him, not always.
Then the Tardis starts translating.
He’s not swearing.
He’s confessing his love for her, while admitting to the Tardis, that he could never actually tell her because how he feels he’s an immortal in comparison to her tiny human lifespan. And even if she didn’t leave him he would have to watch as she turned to dust right before him. He can’t handle that. He was born from her love and he can’t handle the thought of life without her. So instead he rants at the Tardis in Gallifreyan.
And suddenly, Rose understands him better than she did before. And she has a crazy idea that the Tardis all too happily helps with. Slowly Rose learns Gallifreyan.
The Tardis directs her to the relevant books in the library - Rose raise her eyebrows at the titles “‘Gallifreyan for Time Tots’? Really? Superior race. And they called them Time Tots?” but she is all too eager to learn. The Tardis translates the intricate circles into actual words that her human brain can manage. She takes her through the basics and then shows her which phrases she needs to learn. The Tardis helps her with her pronunciation as best as she can.
Until finally, she’s ready.
One day while the Doctor is ranting to the Tardis while doing repairs, as is usual - unaware of the pink and yellow human in the doorway - he hears someone reply… In Gallifreyan. The Doctor is so shocked he burns himself on the exposed wire he had been working on and let’s out a very unmanly squeal.
He whips round to see Rose standing casually in the doorway. She speaks again, he can’t help notice the cockney lilt amongst the melodic words. This time it’s her own confession.
The Doctor had always thought his language sounded beautiful but it sounds so much better coming out of Rose’s mouth.
“Oh Doctor. I promised you forever, didn’t I?” She says, in English this time. Her eyes flashing gold, as her hand cups his cheek. He hadn’t noticed her coming closer but she’s now knelt beside him.
He gapes at her in awe.
“But how…?” He trails off.
She smiles softly at him.
“The Lonely God and the Goddess of Time. That was too much power even for you.” Her smile fades and her hand drops to the grating. “I’m sorry you had to die and it didn’t even work. But the Tardis was as reluctant as I was to let go.” She refuses to meet his eye now. Her expression ashamed as she stares solemly at the ground.
“I’d give up all of my lives for you Rose. I’m just glad your okay.” That’s all he says before he presses his lips softly to hers.
The Oncoming Storm and the Bad Wolf in the Tardis. Together. Forever. As it should be.