Their relationship was, in itself, not so much defined by the rules as it was by the exceptions.

For one-

A Rule: She would never deal with someone who blew her off anywhere near this much, especially without explaining why half the time.

An Exception: Well, when your girlfriend is basically an international superspy and a superhero to boot, you quickly learn that you are not- cannot be- the realise quickly that all you can do is treasure the time you can have with her. You learn to hide your worry when she can't make it, whether she informed you of it or not, because while a normal person may have been hurt, while their may have been an accident or there may be some crisis that they have to deal with, with a hero, you can guarantee that something did happen- that there was an accident or crisis that they are having to deal with and they could very well be hurt or dead and you would never even know until you got the call.

A Rule: If it can kill you, it's probably best to just leave it alone and find something or someone else, or some other method to accomplish whatever it is you're trying to accomplish. Being a coward is sometimes the best course of action.

An Exception: Dating an Assassin was probably not the safest choice in partner, and an Avenger was also, perhaps, not the best for your personal safety. Dating a woman who qualified as both, then, was perhaps most dangerous of all. In the beginning, she was constantly in a state of awareness of the fact that the woman she was with probably knew at least 83 different ways to kill her at any given moment and she was absolutely helpless in comparison. Eventually, however, the thought stopped being considered a potential drawback. After all, Natasha had more than proven that she would never hurt her if she could help it. Not to mention the assassin could easily use those 83+ ways on anything or anyone else they may come across with intentions that tended to be more hostile.

A Rule: If it get's dangerous, it's time to back out.

An Exception: Obviously, this rule was intended more for a situation of potential abuse in some way, but there were other times when it might apply. The first time she found strange men in black clothes speaking hissed Russian in her apartment was the first time she considered the rule potentially applicable. It was by mere chance that the men, who were clearly intending to kidnap her and use her as a ransom for some piece of Stark Tech or another, didn't succeed with their plan. By chance alone did a date happen to have been planned for that night, and by chance alone was Natasha not called away on some mission and therefore arrived just in time to hear screaming and a struggle on the other side of the door. That night was not the first night Dragon spent in the Tower, after Natasha swooped in and saved the day, but it was the last she spent as a guest. When she awoke in the assassin's familiar bed the next morning after a restless night, it was to the sight of boxes of her own personal possessions filling the room and a promise that they could go back and sort out the rest later. Natasha was certainly not going to let her live away from the tower, where she couldn't be around protect should someone attempt something like this again.

A Rule: Don't ever rely on someone else to protect you.

An Exception: After years of refusing to lean on someone, of hiding away from the world because she couldn't protect herself and she couldn't let herself believe that anyone else could or even would, of losing relationships simply because she wasn't strong enough to take any risks and refused to let anyone else take risks for her... She finally found a reason to surrender her list of "rules." She finally let herself trust someone, rely on someone without being terrified of them letting her down. For the first time in far too long, the place that she called home, wasn't dark and isolated... Finally, she found a place, she found a family, where "Safe" didn't have to mean alone.

And for the other-

The Rule: Love is nothing but a fantasy.

The Exception: Who would think that an Assassin could ever find an exception to the rule that she had clung to since she was just a small child. Natasha was sure that the closest she would ever have to that vague, unrealistic concept known as love was with Clint, a man that she considered a little brother, in a sense. But, waking up in a bed, somehow completely at ease as she carefully pulled the warm weight closer, she found that there could be no other cause.

Love was real. It had to be. This could be nothing else.

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Well, that was certainly far more warm-fuzzies-esque than I was expecting. Whatever, who doesn't love fluff, right? As always, I hope you enjoyed, my lovelies, and I will hopefully see you in the next update!