Okay so I love the concept with dragons "mating" and Natsu losing control, so I wanted to do my own take on it. Fair warning this won't be very sexual, so if you're looking for smut look somewhere else. Hope you like it!
Natsu slid onto the barstool beside Lucy and plunked his head down on the wooden table with a small "Oof"
"I'm so bored!" he whined and then turned to face the celestial Mage. Lucy had been reading a blue; leather bound book and writing things down in a small notebook at the same time. Seeing Natsu's pitiful face she sighed and turned to face him.
"Why don't you go fight with Gray? Or Elfman?" she suggested, slightly annoyed by the bothersome dragon slayer. She grinned as she added "Or Erza?"
She loved the way the boy's face paled at the thought of fighting the legendary Titania. "I can't" he replied, "Elfman is with Mirajane and Lisanna doing whatever and Gray and Erza went on a mission. They didn't even invite us!"
Lucy was amused at the boy's childlike face, which was turned into a cute pout. Slightly chuckling she returned to her previous activity.
Natsu huffed as he noticed Lucy turn away from him. You'd think she would have noticed how lonely he looked. His exceed friend was off flirting with Carla and every other team aside from team shadow gear and Gajeel had left. He turned around and rested his elbows on the table with a sigh. He faced Lucy once again hoping for some attention and chuckled at Lucy's expression. She was completely serious as she furiously wrote things down in her little notebook, pausing only to read the novel.
"Whatcha doin' Luce?" Natsu asked and shifted his position yet again so that his hands rested in front of him, clutching the edge of the stool. It seemed his boredom was getting him a bit jittery.
Lucy looked up at him for half a second and then hurriedly stowed the book and notepad inside her bag.
"Nothing." she replied and then started tapping her finger on her thigh anxiously.
Natsu grinned. He'd found something fun to do. He jumped up and started sniffing around Lucy's chair, where her bag was. Finding it lying there, wide open, he lunged. His fingertips had just grazed the shoulder strap when he felt a foot plant itself in the center of his face. His lunge had been stopped short and the bag had disappeared into the lap of the blonde girl.
"Just a peek!" he complained rubbing his throbbing cheek.
"No" Lucy replied firmly, now clutching the bag to her chest.
"C'mon Luce! You know if you don't tell me I'll assume the worst." he continued.
Lucy's eyes narrowed. "What's the worst?" she asked him, stressed that he might guess right. She knew that was irrational though, Natsu guessing anything right was simply never going to happen.
Natsu thought for a moment before answering her with enthusiasm.
"It's gotta be something like writing how bad Erza is at something. Or how she's gonna get fat with all the cake she's eaten!" he declared loudly, sure he was right.
Lucy sighed with relief. The relief that was short lived however as she found a certain swords woman's shadow was now looming over Natsu. He was oblivious to his impending fate as he waited for Lucy respond.
"Fat?" an eerily calm voice asked. Natsu was still assuming it was Lucy as he answered.
"Yes. Huge like a watermelon." and to top it off he sucked in air to make his cheeks big and made arm movements to give the impression of a big person.
Veins had shown up on Erza's forehead and Lucy decided now was the perfect chance to move away from Natsu.
One rage filled punch had been enough to send the boy flying to the roof of the guildhall, releasing the air he had been holding like a balloon.
"Erza!" he screeched, clutching his stomach.
Erza just huffed and walked off to find some of her favorite comfort cake. Natsu was trying to recover from the punch as Gray walked up behind him, half naked.
"Idiot. Why in the world would you insult Erza?" he sneered and stood above Natsu's crouching form.
Natsu was still recovering from Erza's attack so he simply replied, "Your clothes, pervert"
Natsu felt elated as he watched his rival's face take on a look of anger and then shock as he noticed he was showing off his chest and underwear.
"I'm not a pervert!" Gray called as he started scouring the guilds floor for his lost garments.
Lucy had been watching the exchange between the two and was about to comment when Natsu took advantage of her distracted self. Natsu acted absurdly fast as he lunged towards Lucy's bag. This time he got it. Without losing his momentum Natsu rolled into a summersault and jumped into one of the low hanging beams.
"Natsu!" Lucy yelled, grabbing the air below him. A blush spread across her cheeks as she realized he was reading her notes.
"Hmm…" Natsu murmured as he concentrated. You could practically see the question marks popping out of his head.
"Lucy, could you please explain these words?" he asked politely.
Anger and embarrassment laced Lucy's voice as she yelled. "No, I can't. That's why I wrote them down!"
Natsu looked confused as he hoped down from his perch in front of Lucy.
"You mean even you don't understand these words either?" he questioned.
Lucy's blush spread to her neck as she nodded an affirmative. She ripped the bag out of his hands and grabbed the notebook with it. Natsu frowned for a moment, trying to grasp the concept of Lucy not knowing something.
"That's why I copied them down. To learn them. Sheesh. Don't take my stuff without asking first." She explained as she put the notebook back in her bag.
Natsu was still sporting a puzzled expression when he started acting weird. He slowly brought his hands up to his face and sniffed them. Lucy raised an eyebrow at his actions. He kept sniffing and even put one of his fingers in his mouth. A shiver ran down his spine as an odd dreamy expression took over the puzzled one.
"You okay Natsu?" Lucy asked as she raised a hand to check his temperature.
His reaction was immediate as his hand came up to clutch Lucy's wrist painfully. Lucy made a sound of pain and surprise at Natsu's unwanted grip. He snapped out of his trance at the small cry, and pulled his hand away quickly. There were four red finger marks that were going to bruise on Lucy's wrist.
"Luce, I'm sorry!" he shouted, clearly shaken.
"It doesn't matter. Are you sure you're not feeling sick though? We could ask Wendy when she comes back." Lucy said feeling very concerned for the fire dragon slayer, totally forgetting about her own injury.
"I'm fine Lucy. I think I'll take a walk." Natsu replied bluntly before leaving the celestial mage, holding his accursed hands.
Natsu walked out of the guild trying to look as normal as possible. When he broke free of Lucy's stares he started running. He ran for a full six minutes until he found himself deep in the forest near his and Happy's house. Slowly he felt himself collapse on a rock. His hands shook and an unbearable pain had stabbed his head. He didn't care though, a different yet just as unbearable pain flourished in his chest. He stared at his shivering hands.
I hurt Lucy, he thought, I hurt her. He closed his eyes and bowed his head in shame. If anyone else had done that to Lucy they would've been reduced to a bloody pulp by Natsu's hand. But the hand that should've been protecting her had hurt her. It had left marks on her.
Natsu sighed with regret. He would have to look at them the next time he sees her. If it hurt he would ask Wendy to put a spell on her so she couldn't feel it. Hell he'd have to ask Wendy to erase the marks all together.
A bitter feeling replaced the current expression on his face. He brought his hands up and smashed them on a tree trunk for betraying him. The pain seemed to remind him where he was and that the pain in his head seemed to have grown. A lot.
Groaning, he held his head with his bleeding hands and made a mental note to ask Wendy for her diagnoses. In the meantime he put up a brave face and went to vent his anger on Gray.