Summary: Jacob Black, a secret shape-shifter and expert in bonding and mates. Edward Cullen, a vampire who thinks he has found his mate in Isabella Swan, who is incidentally Jacob's best friend.

Knowing the ups and downs of bonding, Jacob is against it and tries to intervene as much as he is able to without actually meeting the Cullens.

But when he had befriended the vampire through his cousin, Harry Potter without even knowing he was the same Cullen he was trying to get Bella to stay away, all sorts of problem began to arise. Not all is what it seems and his small problem and personal appointed mission of protecting his best friend from Edward Cullen may be the least of his problems.

Note: Unedited. No beta. Slash. Slow update.

Theory of Bonds

01:

He had known that the supernatural existed. He had seen it personally. He had lived with someone who had powers he was in awe with. He knew he wouldn't be able to have that particular ability. It was simply not in him. He had already accepted that.

That didn't mean he had completely erased his heritage from his life like what his dad had done. His dad didn't even seem to be interested in that world and hadn't told or even given a clue that he knew about it. It seemed he didn't want his children to know. So in turn, he hadn't said anything when his Aunt had contacted him while he was still a seven-year-old kid.

There were supernatural stories that had existed in the Reservation about shape-shifters and cold ones. About moon wolves and animal protectors. He had researched about it extensively whenever he visited his Aunt without his family's knowledge ever since he had heard of the stories.

Because he knew that was the only time he would ever know about the complete truth about the stories. He already believed them when he knew about Wizards. After all, if there was magic, surely, there's also those supernatural creatures.

And then he turned out to be one of them.

It was a good thing he already knew about them, or he might have done something reckless when he found himself being transformed rather painfully without any sort of explanation and more importantly, help that time he was in England. Jacob was just glad that his Aunt and an acquaintance of hers helped him with his rather abrupt transformation.

Researching about his sudden condition had made him understand what made him become a shape-shifter. He understood all it was that was needed in his kind – his very nature, his wolf and imprints – and the cold ones or vampires that triggers the change.

He understood himself even before he arrived back in the reservation after his month stay with his Aunt that he excused with his dad as free travel he had won. He returned with the full determination that such a thing, that he being a shape-shifter would only be known by himself and no one else. It wasn't just because he trusted no one, not even his own father – because he didn't know if the stories circulating the Reservation were just that, stories or real for them – but also because he was apprehensive. Apprehensive of what might happen when his transformation became known.

Because from his research after his first change, a wolf needs to be a part of a pack. He knew from the limited books and texts in the school library to further his research that having a pack stabilizes the sanity of the werewolves and shape-shifters. From his experience, he never had a lapse in sanity. Maybe the first few times of his transformation sure but not afterwards. So he frankly didn't think he'd need a pack.

And besides, the connection between all the pack members weren't such a good thing to him. The link sounded intrusive. It didn't give him any privacy. With this information, he was for sure, having a pack would only hinder him in the long run.

And so, no one knew him being a shape-shifter. Not his father, his friends, the people around the Reservation and Forks, and certainly not the shape-shifters that had suddenly changed after him that Sam apparently leads. It was his very well-guarded secret.

Well, up until his childhood best friend, Isabella Swan arrived.

. . . . .

"Jake, do you know the Cullens?"

Jacob stopped what he was doing. He slid out of the car he was repairing and stared at his best friend. It had already been a week since Bella arrived and like in their childhood, they instantly connected after a few talks.

It didn't even seem as if they separated for years. They just clicked.

"The Cullens?" He asked. He did not particularly have to stop repairing the car but he had heard the odd inflection in Bella's voice when he spoke of Cullens.

Normal humans would not have been able to catch it but with him being a shape-shifter, his hearing and senses were superior to that of humans.

And he always used that fact to his advantage every time.

Contrary to popular belief in the Reservation, he wasn't naive, clueless, or stupid. He just did not have any reason to act on what he knew. He might be a bit oblivious at times but he wasn't stupid.

And sometimes, acting as if he did not know anything gained him loads of information.

So he stared at Bella in confusion, half confused yet half knowing.

He knew that the Cullens weren't exactly human. Like he had said, he was not stupid. He already knew that they were the cold ones told in the tales, the vampires. The reason why the werewolf gene that others possessed awakened. And Isabella Swan, his best friendwas a human. Any humans, no matter how clearheaded and intelligent they were, could be rather taken with the beauty and allure vampires carry.

It really was no surprise that Bella would have interest with them.

Though he wished that wasn't the case, but he knew that he was correct. But he didn't know why she was asking him about them. He lived in the Reservation while the Cullens lived in Forks.

Bella nodded while she looked at him with a slight innocent smile. "Yes. I met them in school. They are so mysterious. It makes me want to know them even just a little bit,"

"Bells, it's better to not have anything to do with the Cullens," He stood up and took off the gloves he was using from his hands and placed them onto the hood of the car. He faced his best friend who was looking confused at him.

"Why? Do you know them?"

"I don't. Do you see me leaving the Reservation at all?" When Bella opened her eyes with that mischievous smile on her lips, he added with a smirk. "Aside from your house and any other stores that I needed to go. I don't wander around Forks without reason Bells. And I never encountered them,"

Bella pouted before giving him a questioning look. "Then why? Did they do anything that can be considered as bad?"

'If you count being a vampire as bad then yes.' Jacob wanted to say but of course he didn't. He had some sense Thank you very much. As much as Bella was his best friend, he couldn't have her learning about the Cullens at all. Not only because it would threaten his own self but also because knowing would lead Bella right into danger.

'But then again, they couldn't help it if they're vampires…'

"Not really," he tentatively said. Bella gave him an arched look that clearly said to explain. He sighed. "I just think you should stay away from them. They're anti-social from what I heard,"

And that was true. The Cullens had never socialize much with humans. They do it from time to time, but only when it was needed. No more, no less. From what he had observed – since he was curious why the shape-shifters who seemed bent on killing any vampires hadn't harmed the Cullens yet – the Cullens and the shape-shifters of the Reservation had a treaty.

Cullens had to respect the boundaries between their kind and they wouldn't drink nor turn any humans. That was all he had concluded though since he couldn't outright ask or research about it. No one from the Reservation knew about him after all.

"They might be that, true. But they're not harmful," Bella stated as though she was speaking of fact. He resisted the urge to snort. "And they're extremely handsome and beautiful! You should see them Jake!"

Jacob rolled his eyes as Bella continued her tirade about the vegetarian vampires he really didn't want to see nor meet.

He hoped that Bella's fascination about them fade in time.

. . . . .

"How are you holding up there Jake?"

Jacob groaned as he stared at his ceiling inside his room while his cell phone was pressed on his ear. Just hearing the quite chirpy voice of his cousin was making him feel tired, even if he was curious why Harry sounded happy when usually, he didn't sound like that when they talked a week ago.

"Bella is infatuated with the Cullens," he stated softly.

"Huh? So? Don't tell you like her," Harry questioned. He took on a disturbed expression. Bella was like a best friend/ sister to him. Just thinking of her like that made him felt like he's into incest.

"I don't. It's just that…" he lowered his voice a little to not be heard since he knew shape-shifters have patrols around and he didn't want to risk being heard. "Their vampires,"

"Muggle kind or magical?" his cousin asked abruptly, voice all business-like, devoid of any cheerfulness. He wetted his lips in apprehension.

"I don't know. I've never seen them under the sun and I've never wanted to get close to them," he heard a sigh from the line.

"Of course they wouldn't. Well, it's good that you didn't. Vampires of all kinds sometimes get abilities. Do you know if the Cullen coven have any with them?"

"No. Like I said, I never bothered. I didn't think I have to investigate since I never really went out much. And abilities? What kind? It wasn't stated in any books I read," Harry snorted.

"Of course they wouldn't state about it. Vampires controlled that information. They don't tell about they're kind for protection. Witches and Wizard here do want to kill any dark creatures you know,"

'Along with me' he thought, grimacing a bit. For them, shape-shifter being a cousin of werewolves mean that they were also dark creatures. Never mind that they're ability was like an animagus one. Idiots just like his cousin always said.

"And abilities... like causing pain and senses deprivation. I've seen that ability with the guards of Volturi, Jane and Alec. Fire, electricity, strength. Concentrated powers that witches and wizards could do you know. Only, they either have one or nothing,"

"That's cool. I would have wanted one of those," he grinned, though it was clouded with the knowledge that it could be used on him. Frankly speaking, if Jane and Alec weren't a part of the Volturi guards, They wouldn't have stayed in power. But that's just his thought.

And Harry too. Good thing they would never be meeting any Volturi anytime soon. And that if he did, he had Harry as his ally.

He heard Harry laugh and he grinned. But then they're mood turned somber again when Harry spoke quite seriously. "Just… be careful Jake. You're a shape-shifter now. Natural animosity between your kind and vampires weren't recorded but you're still a cousin of werewolves. It might be there," he cautioned. Jacob blew his breath at that.

Yeah, werewolf and vampire couldn't ever be mixed because they were naturally enemies. In case of shape-shifters, he didn't think that was the case. The shape-shifters in the Reservation looked and felt like they didn't like vampires because they were the reason why they changed.

And for the vampires? Who knows. Certainly not him. Like he said earlier, he didn't bother investigating about that.

"Alright," he just said.

"Okay. I better go. I have to go to Gringotts to look through my vault. See if I could give a good wedding for Ginny," Harry happily announced. He could practically hear his grin as he spoke. He smiled.

"I'm happy for you," and he was. Even if he didn't think this Ginny person is good for him. From his cousin's stories along with her photograph, this Ginny looked an awful lot like his mom. Minus the eyes. Wouldn't Harry pause at that? And this girl sounded like a fangirl that tried to catch her man pretending to get over her fangirling.

But then again, that's just his opinion. And when Harry went mad at him for telling that, he never said another negative word towards the girl.

"Thank you. You're coming right? I have to introduce you to them in the wedding,"

"You didn't tell them about me?" he asked with his eyebrow raised.

"Uh… no. Only Andy, Remus and Teddy knew about you. I wasn't about to expose you to the rest of the prejudiced Wizarding World. They might think less than honorable things to get to me. You know how they think about squibs,"

He nodded to himself. What his cousin had said was true after all.

"Okay. Get on with your self-appointed task,"

"Then sleep already you oversized dog!"

He chuckled as he cut off the call.

. . . . .

Jacob heard about Bella's accident from his own dad.

If he didn't know that the Cullens had rescued her and was probably with her or even watching her, he might have gone to her almost was, he didn't want the Cullens to know, much less even see him. So he contented himself with calling Bella at that precise moment.

"Hi," Bella greeted rather calmly and unconcernedly. He stared at his phone for a few moment in disbelief before he brought it back to his ear.

"Hi? I found out you almost died just a few seconds ago and all you want to tell me is 'hi'? Bella, are you insane?" he couldn't help but say incredulously, voice almost shouting in slight distress.

Really, Bella has apparently no concept of tact and self-preservation.

"I'm okay Jake. Where are you?"

"I'm in my school obviously. I had to excuse myself from class because I just had to know what happened. Bella, I know you're a careful driver and I know Charlie put some snow tracks for your tire. I helped him last night. So how could you be in a car accident?" he ran his hand through his hair – a habit he picked up from Harry on his month stay in England.

"A classmate's car slipped from all this snow. It almost hit me if not for another's help," Bella explained. His head created a scenario he didn't ever want to witness himself because he could feel his wolf inside growling as they already considered Bella as their pack mate.

"Slipped? What, did he drive fast in this kind of weather?"

Bella didn't bother answering him and he also didn't bother pausing. It seemed like such a huge waste of time because it wasn't important. Not at that moment. Though…

"This classmate of yours better not let me see him Bells. Such a stupid thing to do! Are your classmates idiots?" Bella just laughed freely, as if she wasn't concerned about his almost death anymore. He sighed. Really, Bella's such a forgiving person. It's almost annoying.

"So, who helped you?"

"Edward Cullen," Bella teased. He didn't have a mind reader to know what was inside Bella's mind. She's probably thinking that I was such a suspicious person thinking the worse out of people. Look at how a member of the Cullen family helped her.

Still, his eyes went wide. A vampire helped? A human?

He didn't think he was prejudiced and he also liked to think that he would never judge a person base on what they were. The Cullens were vampires and a vegetarian to boot. As long as they didn't give him a reason to dislike them, he's okay with them.

But vampires were dangerous in general so it wouldn't be bad if he could be a little wary with them, even to a coven as nice and unconventional as The Cullens.

"A Cullen? The one you're so interested in?" he shot back in reply. Bella started coughing on the line and he smirked a little, knowing that she was probably blushing horribly. Let it be known that he could also shot back when attacked.

"Jacob!"

"What? It's true!" he protested with a smirk still on his face.

"They're here in my room, idiot!" she hissed in embarrassment. He choked on his own spit. Logically, he knew that they would be there with her, probably even the entire school student. He just didn't know that the Cullens would be there inside her hospital room. With them being a vampire, they're hearing senses were also superior to that of humans so even in the telephone, they'd be able to hear what he was saying to Bella.

Goodness! Why didn't she told him before!

Though now that he thought about it, the situation Bella was in now was funny. He almost laughed if he hadn't controlled himself.

He heard in the background some chuckles and a slight laugh, but they're too soft for human ears. But with him as a shape-shifter, even if it was just on the phone, he could still hear it. His wolf had an exceptional smell and hearing and it transferred to his human self.

And what were they doing there in the first place? Because Edward Cullen helped save her? Wouldn't the doctor not allow anyone other than relative inside?

"Miss Swan, we have to conduct some further test to make sure you're okay,"

Oh. He knew that voice. It was Carlisle Cullen. If he remembered right, he was a doctor. Quite an unusual job for vampires, but then, Cullens were probably the embodiment of unusual. Imagine a vampire attending a human school? He shook his head at the absurdity of that idea.

"I'll talk to you later, okay?"

"Right. Should I come or..."

"You come. I don't think dad's gonna let me go anywhere after this,"

He chuckled. That was true.

"See you later then,"

After hearing a confirmation from his friend, he turned off his phone and waited for the hour to finish. He decided to just attend the next class since he's already extremely late anyway. Might as well not attend at the moment.

Though he knew that he would probably be called by his advisor later due to this absent. He sighed.

Well, he'd just have to face the consequence of his action. He just really hoped Bella's okay and that her still apparent curiosity for the Cullens diminish for the next few days.

He doubts that though.

A/N:

And here's first chapter of my first-ever Harry Potter-Twilight crossover. This will of course contain Slash and possibly a threesome. I'm still undecided. Oh well... Hope you like this new fic of mine.

Anyone who wants to read VK fanfic, visit my other profile. Username's ReeveRegala. Cya!

Review!