Lannisters weren't supposed to love Starks. Especially during war times. But, how could he not love you?
When he first met you, he couldn't eat. He was too full of love to even look at food, which made him feel ill. He hated how it felt; but he couldn't get enough. You were too sweet, so sweet he'd get a toothache when he'd kiss you.
So, when he went to go fight— against you and your family, he was deeply depressed. Part of him knew it was his duty to fight for his family, but- his love for you transcended his duty. However, before he left- he promised you something. That no grave would hold his body down, and he'd come back.
After a— particularly difficult battle, he was left injured and practically almost dead. Yes, they were your soldiers, but- he didn't care. He would crawl home to you, no matter the situation.
And that's what he did. The second the battle was over, he came to see you. He was severely wounded and could barely walk, but he made it. He arrived at the castle and entered your chambers.
He instantly crumbled onto the floor in front of your bed, causing a bang. You sat up, confused and half asleep.
"I told you I'd come, didn't I?" He says out of breath, smirking.
