Natsu wasn't sure when it had started. No, that was a lie, he knew when he'd first felt it, that stirring somewhere deep inside. It had been when he had faced Laxus during the Battle of Fairy Tail, realising deep down that he was more than outmatched, and still facing him, still fighting, even when it had hurt to breathe let alone move. Even as some small traitorous part of him had recognised the pain in Laxus' expression, the searching for a place to belong that Natsu knew all too well. Igneel had left him behind, and Ivan…well the last said about the other Dragon-slayer's father the better. They were so similar and so different, their pain given different forms and some part of Natsu had realised it at that moment, but there was nothing he could do. Laxus wouldn't hear his words, and as much as part of him wanted to help, the guild had to come first, and so he fought and won, desperately trying to make Laxus understand that the guild was family.

That they were family.

In the end, he knew that he'd got through, but it had been too little too late. It was why he had fought against Makarov's decision. Couldn't Gramps see that they were one and the same, that with another push or two, their places could have been reversed? Maybe not, Natsu wasn't sure he could have ever had that much rage, but he understood, and he could smell Laxus' pain at his punishment, a sourness in the air that curled his stomach, and left a knot of something lodged in his chest.

He didn't watch Laxus leave, a decision that he would later regret. He knew that the other Dragon-slayer had seen the Fantasia parade though, had caught his scent, still soured and now with a tang of salt – tears on the wind – and when he had held his fingers up high, it had been Laxus that he had been searching for. A promise that they would see each other again. A promise that Laxus could come home. A sign of something to come that he had no words for, that was little more than a tentative flutter in his chest at that moment.

Life moved on.

Fairy Tail was never a guild to sit still, even after something that had pitted themselves against one another, and for a time Natsu was swept along with it. He laughed and fought, went on missions, bickered with Gray, and tried not to think about Laxus.

At first, it was little things, the distant rumble of a gathering storm that would bring him to his feet, eyes searching for the familiar figure of the other Dragon-slayer. He'd never been bothered by storms, even as a child he had loved watching them, standing out in the open and daring the lightning to strike him until Igneel would drag him back into the shelter of his wings. Now, he chased them. On jobs, he would slip out on stormy nights and find the largest empty space he could, arms spread wide, as though if he made himself enough of a target, Laxus would find him. He never did, and the others would look at him askance when they caught him slipping back in soaked to the bone, and deflated, and he couldn't answer their questions, because he didn't know the answers. Why? Why do I want to see him so much? He asked himself that over and over each time, and yet he was no closer to an answer, he just knew that he wanted it. It didn't run as deep as his need to see Igneel, but he wasn't sure if that was only a matter of time, feeling it pool in the pit of his stomach, deeper and deeper as the weeks stretched by.

Then there were the dreams. Natsu had always had an active imagination, he had often amused Igneel with tales of his dreams as a child. As he grew older, those dreams shifted, echoing his never-ending search for his foster-father, his need to protect his new family, and ghosts of what he had lost. Now, he dreamt of thunder and lightning, and a warmth that didn't come from the fire in his veins. Sometimes he flew through the storms, a dragon finally given flight as he chased something…someone…Laxus. Other times he was on the ground, on a wide-open plain, a sound he didn't recognise – something far from human – welling in his throat, louder than the thundering roar of the storm above his head.

A cry.

A call.

A plea left unanswered.

Each time he would wake with a start, a hollow feeling in his chest, as though he had left a part of himself behind. As though he was incomplete, and when he tried to work out what was missing, all he could hear was the pounding of his heart and the distant echo of a storm.

Time crept on. Edolas happened, and Lisanna returned to the guild. For a time, Natsu forgot about the storms, the dreams, and the hollowness. He laughed and celebrated having his childhood friend back, his family almost whole again. Almost. Because Laxus wasn't there, and he didn't know why that bothered him so much, but it did, niggling at him. A whisper at the back of his mind. A flutter in his chest. An itch beneath his skin that he couldn't reach. The dreams returned, the need to chase the storm haunted him once more.

He knew that the others had noticed.

Erza was watching him more than usual. Lucy even went so far as to invite him to sleepover several times a week, never complaining when he woke from his dreams, gasping and hollow, staring out into the night as though he expected to find Laxus walking up the road. Gray fought with him more often, pushing him, whether to exhaust him or to try and get him to open up he wasn't sure. While Wendy stayed close, and more than once, he caught her hands glowing and hovering close to his body, as though expecting to find something to heal. He didn't want to worry them, but he couldn't bring himself to tell them about the dreams, about the longing, the almost physical need for the storm. A hunger that was consuming him a little more each day. So, he avoided their worried looks and questions, he fought Gray, he brawled with the guild, and he dreamt of thunder and lighting.

His first flicker of understanding came in the wake of the 'Daphne' incident. He was shaken, past and present blurring more than he wanted to admit. He was angry at Gray, but really, he was more furious with himself, because he had come so close to losing himself, to losing control of the magic that Igneel had given him and turning it on his friends and family.

That night there had been flames in his dreams. At first, he thought the lightning had struck something, a tree, perhaps, and he had quivered. That was something new, something closer… was Laxus coming? Something had shifted in the darkness, something large and burning, an echo of Igneel looming over him, and for the first time, Natsu felt disappointment at the sight of his foster-father. Even though he knew that this was a dream, that if he reached out, it would fade away, as allusive as the Dragon-slayer, he chased in his dreams. He didn't reach out, keeping his hands clenched at his side, head bowed beneath the weight of the Dragon's gaze. Waiting for the chastisement, the disappointment at how close he had come to losing. Unprepared, for the feeling of the giant muzzle brushing his head, nuzzling him with the rare tenderness Igneel had shown him after a nightmare, or when learning to master his Dragon-slaying abilities had felt impossible. His breath caught, tears prickling the corners of his eyes.

"Igneel…?"

"Find him." It was Igneel's voice, the rumble of lava beneath the earth, the crackle of wildfire, but it was distant as though the Dragon was speaking to him over a great distance. When Natsu looked up, he realised that the image was fading, the fire slowly being extinguished by the storm whipping around him.

"Find who?" Igneel, or… He wanted to find both of them, and there was no way that Igneel could know about Laxus, about the longing that even now had him wanting to turn away from the fading image of the Dragon and search the skies.

"…Mate…" The word echoed, almost lost as thunder rumbled overhead. Lightning flashing overhead, blinding him for a moment, and when his vision cleared, Igneel was gone, leaving the echo of his voice, a memory dancing just out of reach.

Mate…

It was days later when he was collapsed over the side of the deck, stomach turning itself inside out as they sailed towards Tenroujima that he finally connected the dots. Mate. Igneel had mentioned it once, a long time ago, and Natsu had barely paid attention because it hadn't been about fighting or magic. He'd encountered a girl from a village near when they had landed for him to find food and water, and unused to other people, he had all but bolted back to Igneel. He had been afraid, but unwilling to admit it, and he had feigned disgust as only a child could, telling his amused father that he didn't want to play with a 'girl'. Igneel had laughed and brushed his head with his muzzle just as he had in the dream and told him that might change one day. To which Natsu, stubborn even then had said 'never', wrinkling his nose when he remembered Igneel trying to tell him about the birds and the bees – although he still wasn't sure what it had to do with birds and bees.

When you find the one, your mate – whoever they are, male or female, that will change, Igneel had told him amused, but soft-voiced, laying his head down so that he was eye level with Natsu. No Dragon can resist their mate, not even me… There had been a touch of sadness in his words, but at the time Natsu hadn't noticed, declaring that he could and would resist it because he was going to be the most powerful Dragon ever.

How wrong he had been.

Mate…

…Laxus?

Something subsided in his chest, as though it had just been waiting for him to connect the dots. He still felt the longing, a siren call that he couldn't answer, an itch he couldn't escape, but it had eased a little. Mate. He clung to that thought, to the echo of thunder in his mind for the rest of the journey, a small part of him hoping that if he succeeded, if he made it to S-Class, then maybe he would finally be able to find Laxus.

Laxus was there.

Natsu had felt the gathering storm, even with the chaos around him, the pain from his wounds, the exhaustion that dogged his steps, growing with each fight. It tingled, making the hairs on the back of his neck stand on edge. Mate. It wasn't a dream this time. It wasn't distant. The storm was coming, closer and closer…and then everything was falling, Natsu was falling, defeat looming, and the lightning came for him, as the other Dragon-slayer materialised in front of them. In front of him, the world, his friends and Hades fading away for a moment, everything narrowing down to Laxus as the other Dragon-slayer straightened. Natsu could see him, smell him, and he wanted nothing more than to reach for him, to calm the itch beneath the skin, but there was no time. Instead, he watched, relieved as Laxus attacked.

It hadn't been enough. Laxus was down on one knee, admitting that he couldn't win this fight and Natsu had stirred, flames rising, refusing to lose the storm now. To lose Laxus when he was finally there. He shouted, not sure what he was saying, breath catching when blue eyes met his. There was a world of emotion in that single glance, an echo of the longing that plagued him, a plea and determination.

The lightning was a surprise.

It wrapped around him, and the itch beneath his skin surged to meet it and for a moment all there was the storm, and he was part of it, as Laxus' magic wrapped around him. Understanding dawned, and he devoured it. It had never worked before, but this was different. They were different. Mates. The lightning settled beneath his skin, and for the first time since the fight at Kardia Cathedral, he felt at peace. Everything was still balanced on a knife's edge, they had to win there was too much at stake. But Laxus was there, injured, and out of the fight, but there. His magic merging with Natsu's until it felt like they were one, and finally feeling whole, Natsu stepped forward with a growl, fire and lighting crackling around him.

The fight and the aftermath were a blur, everything hurt inside and out, exhaustion pressing in on him from all sides, but beneath it all, contentment purred in his chest. Laxus was here. He had been pulled away, first into a reunion with the Raijinshuu. That Natsu hadn't minded because Laxus was still in sight, and he was being swept up in the celebrations too. Then the other Dragon-slayer had been pulled away to talk to Makarov about the fact that he had turned up on Tenroujima when he was no longer a member of the guild, and Natsu had felt a shiver of fear at the stern look on the old man's face. Not again, he thought, and he might have followed them, if Laxus hadn't glanced back at him, mouthing at him to 'wait', only the echo of his own uncertainty making Natsu heed his words.

Time had never passed so slowly.

He was reasonably sure that Erza had connected the dots, looking between them, and smiling in a way that promised trouble for him before following Laxus and Makarov into the trees. He paced, exhausted and antsy, wanting to join the ongoing celebrations or sleep for days, Laxus' magic still lingering beneath the surface, a soothing presence. A tingle, a promise. Gray and Lucy tried to talk to him, but he was shifting from foot to foot, restless and unsettled, the storm pressing around him and yet still out of reach.

What was going to happen if Laxus wasn't allowed to return?

He hadn't let himself consider that on the few occasions he had allowed himself to try and imagine what would happen when…if he ever found Laxus, and now it loomed over him. Could he let Laxus go again? Would he follow him? He didn't know the answer, but he understood what Igneel had meant now. The longing, the need to see him, it was overwhelming. He was just turning, ready to march into the trees and find the other Dragon-slayer when a shadow loomed over him, the smell of the storm, the scent of Laxus washing over him even before he lifted his head to meet blue eyes. He hadn't planned for this moment. Hadn't worked out what he was going to do when he was actually face to face with Laxus without danger breathing down their necks, but the longing, the siren song of the storm pulled him forwards. Closing the distance between them, a rushing sound in his ears, his voice sounding strange to his own ears as he asked.

"You're staying…?" Please… There were hands on his shoulders, the storm engulfing him, and he wasn't sure whether the rumble of thunder was in his mind, or around them, but beneath it as clear as he heard the pounding of his own heart, he heard Laxus reply.

"I'm staying."