He left her and went back to his chamber. His heart couldn't stop beating faster when he was rethinking about their moment in her solar. The things he wanted to do to her but he couldn't. Never in his life didn't want so much to touch a woman, to be buried so deep inside her untill he loses himself. It's ironic that this woman had to be his half-sister. If he allows himself to take her, they will become just like the Lannisters.
He has noticed how Sansa was looking at him. Expectantly, always trying to figure out what they have, what does that unresolved tension between them means. He could show her how much he wanted her but too many obstacles are in the way.
He feels so wicked sometimes. What is wrong with him? That is his half-sister starring in these indecent thoughts of his. He thought of her hair, her body, her voice.
His hand dropped to his breeches. He grabbed his cock and started pumping it. He fantasized his hands were Sansa's pussy walls, squeezing his member and clenching it so tightly, he couldn't breathe. Stoping abruptly, he removed his hand and pulled himself together. That would lead to nothing. There was only a person it could fill the void he was feeling.
Seven hells, he needed her. All the things he wanted to achieve were all for her. No point of being King if she wasn't next to him, as his Queen. He fell in his bed and put his arm above his eyes. Drowning in his fantasies of her, at some point deep sleep took him.
The next morning he decided to go to the crypts before he departs. Dear old Ned, wish you were here, he thought. At least, you would protect her. Lost in his own thoughts he didn't hear footsteps approaching.
That creepy bastard Littlefinger. He wish he could take his eyes out just because of the way he was looking at what was his. He tried not pay attention to what he was saying but he was making it hard. And then he spoke of the words he wasn't even able to say himself.
"I love Sansa. Just like I loved her mother..."
Something snapped inside him. Grabbing the man's neck he pushed him to the wall. He could easily break his neck but he didn't.
"Touch my sister and I will kill you myself". He threatened. He took his fingers from his throat and exited before he would do something worse. He walked to his horse and jumped up his back when he felt someone watching him. Turning his gaze he met hers. Did she woke so early just to see him leaving?
That connection he felt to her was stronger then ever. His heart was pounding faster as he drunk her form for a last time. He waved goodbye and pushed himself to go. Some part of him, probably his heart, stayed there in Winterfell.