I actually wrote this with a lot of inspiration from Beejette, who has written some other John/ Jo pieces that I love. But she's stopped publishing on this site and that makes me very depressed.

So, this takes place in a 'verse where Jo asked John to teach her to hunt and they're on the road together. The 'verse belongs to Beejette.

It was impossible to not be intimately –to a truly painful level—aware of each other's habits and quirks, living on top of each other like they did.

He drank coffee twenty four hours a day. First thing in the morning, right before bed, on every stake out, at every meal. It was always black and bitter. If Jo were more poetic, she might appreciate the special sort of symmetry in that. But Jo just wrinkled her nose as he guzzled the stuff, collected the seemingly endless trail of empty coffee cups from gas stations and diners that seemed to gravitate around him when he was in research mode and she learned very early on that if she finished the pot of coffee she damn well better brew another or suffer the grouchy wrath of John Winchester.

Likewise, he learned that if he wasn't proactive, Jo would use her unnamed psychic powers to locate any remote of any room in every motel in the country. If she had her way (and she had a special knack for getting her way) the TV would never leave the Bravo station, not even while she slept with one hand on the knife under her pillow and one hand gripping the remote tightly enough to whiten her knuckles. John knew exactly what was happening on the current season of Project Runway and he would never forgive Jo for that.

He could be a possessive bastard, especially when he drank.

It wasn't her fault that all he wanted to do at a bar was sit like a lump and get impossibly plastered. It wasn't her fault that vodka made her want to dance and tequila made her want to sing and whiskey… well, whiskey made her want to get naked and rub herself against the first thing with a dick and an easy smile.
John would tolerate her flirting with young men, taking the drinks they bought her, watching her run her fingers over their arms, like she might, maybe. But she always ended the night on her back or on her knees for John.

He had known, from the moment she climbed into his truck, that she would wind up in his bed. He wasn't proud of it. God knew he wasn't going to pursue her, but the laws of men and women, close quarters and adrenaline didn't have exemptions for dirty old bastards and the barely legal daughters of old friends.
It happened between La Push and Topeka, a Poltergeist and a Werewolf. John had missed, John had mother fucking missed, and the Poltergeist blew right past him, unwavering in its ugly focus on the pretty young blonde.

Why were those fuckers always so focused on the pretty young blondes?

Jo hit the ground, metal scraped against concrete as the gun flew out of her hands and the hideous brute ripped into her taut skin like it was butter. The air smelled like iron from her blood and John, honest to a God he didn't believe in, thought she might die.

She let him help her to her feet, but then batted his hand away, shooting him a juvenile glare that said 'I can do it myself.' She stitched herself up with all the stubborn resolution of a toddler dressing themselves for the first time but when she took off her shirt to pour straight whiskey on the fresh stitches, there was very little child about her at all.

Blood, stitches and whiskey should not have been an aphrodisiac, but John's cock didn't get the memo. She smiled that knowing smile at him, a cat who had figured out how to finally get the canary, and then sauntered towards him, all swaying hips and pouting lips. She was in front of his chair, leaning over him, pushing her youth and her beauty and her sinfully pale skin into his face, daring him to take the bait.

But John Winchester didn't take bait and when he finally fucked her, he vowed that it would be with her begging for his cock on her knees.

John stayed stony, pretended that he didn't touch himself in the shower, thinking of her hands, Jesus, her lips, wrapped around his hardness. Pretended that it had never crossed his mind in the night to climb into her bed and shove her knees apart and just take, reducing their relationship to nothing but the fundamentals of man and woman. Jo reached behind him. She retrieved a clean shirt and snagged the keys to his truck, explaining herself as going "out" and shooting him a look telling him not to wait up.
Of course he followed her, because she was young and reckless, especially when she had something to prove. He followed her to a bar where the oldest patron was probably twenty five and she was sandwiched between two kids wearing labels that only their parents could buy for them. The music was pounding and the strobe lights were flashing and John didn't tear his eyes away from her as she rubbed her ass into one boy and rubbed her breasts against the other. She knew he was watching because she was staring right at him.

A child, showing him all the toys he couldn't play with.
The kids puffed up their chests when he marched onto the floor and pulled her away, but their bravado was shot down with a cold glare. John Winchester looked Hell in the eyes every day, a bar fight with a twenty five year old didn't even phase him. Maybe the kid could see the death and suffering and violence in John's face, even with the thumping music and the blinking lights. Maybe the kid really was all show and didn't want to rip his Lacoste polo. Or maybe the kid, like most people who saw him and Jo together, thought that he was her father and didn't want to even go there.

He was careful of her fresh stitches as he slammed her into the back of the motel door when they got in. He was conscious of her injury, even as he crushed his lips against hers. She could taste the alcohol on his breath, but this had been a long time coming and they both knew it.

He took her on her back that first time, one leg thrown over his shoulder so that he could sink into her, all the way to the hilt of his cock. She was ravenous. A woman's hunger for sex with all a child's demanding.

Neither was surprised the next morning. Nothing had really changed between them, after all. Nothing that anyone besides them would notice. Jo woke early and started a pot of coffee for him. John turned the channel to Bravo without her asking.

Everyone had assumed that they were fucking, long before it even happened. John Winchester and a beautiful young woman? Any idiot could have guessed what would happen when the two of them were alone, locked behind the door of an anonymous motel. Reactions varied; some wrinkled their nose at him, but some hunting friends smiled knowingly, patted him on the back and asked him vulgar questions. They wanted him to confirm the filthy rumors they had heard, hungry for details so that they could stroke their cocks at night and pretend it was them fucking little Jo Harvelle into the mattress, against the wall of a bar restroom, in the front seat of his truck.

It didn't matter that half the rumors weren't true; John was adventurous and Jo had a wicked imagination, but neither could fathom the fantasies of gin soaked middle aged men who had only the company of a centerfold most nights.

Hotel staff sometimes shot them weird looks. Jo wasn't quiet. Usually their first night would kill any assumption of a father-daughter relationship, or at least a father-daughter relationship that wasn't ten kinds of fucked up. She wandered around to the vending machine in skimpy tops, displaying his love bites for the world to see. He still wore his wedding ring. The longer they stayed in a single place, the more attention they got, so it was a damn good thing they never stayed still longer than it took to burn some bones.

Sometimes he would catch her staring at it; the little gold band that promised his heart to a dead woman. She was petulant, stubborn, reckless and rash, but she wasn't an idiot and she never said a word. He was grateful for that.

She could get him hot faster than any woman he'd had in a very, very long time. He never laughed or smiled, but when he did –fleeting as it was—it was because of her. She was blonde and vivacious. She slept in his arms at night and kept his unspoken secrets but she wasn't Mary. She would never be Mary and John never wanted her to try.

It was selfish. She was a beautiful girl. She was a brilliant girl. She was a goddamn force of nature when she wanted to be. She was the kind of girl that any man would be damn lucky to call his girl, but John was old and jaded and he didn't have it in him to love her half as much as she deserved. At the same time, he didn't want to watch any other man love her.

It would end badly.

The best case scenario would be her waking up and realizing that she could do a whole lot better than some grouchy old bastard. She would tell him that she didn't want to fuck him anymore and march out of whatever motel room they happened to be in that week. And he would put up a fight because he was a greedy asshole.

The worst case scenario would be that one of them would wind up six feet under.

John didn't have it in his heart to carry the torch for two dead lovers. Jo deserved to be immortalized in a cold golden ring. Jo deserved to leave behind a wreck of a man, dedicating his life to her revenge. That man would never be John. His plate was full of the unrealized justice of his dead wife. He couldn't dedicate his life to avenging his dead girlfriend too.

It was a mark of how fucked up their lives were that John measured her worthiness by how she deserved to be mourned, but John never pretended to be anything other than fucked up.