AN: This was a request from millennial-star-gazer on tumblr. :)

"Heightened"

Rated M for smut.

Summary: After eating a potion-infused chip he bought from some sketchy clerk, Natsu is thrown into Dragon Force. Lucy quickly finds that it isn't just his appearance that is affected. With heightened senses, the boy is possessive and territorial over her.

Heightened

"Sir, could you perhaps be a dragon slayer?"

Natsu's ears perked at the question. He and Happy had been traveling home from one of the jobs that they went on together. Even though they loved the rest of Team Natsu, the two still chose to do some jobs alone to spend some time together.

Natsu nodded at the man behind the counter. They were currently in a magic shop, looking for any keys that they could bring back to Lucy.

"Yeah, I am. Why?" he asked.

"I have something that you might like," the man answered. "But first, do you have a partner?"

"Partner?" Natsu immediately pictured Lucy. "Yeah, I do. Why?"

"Because I can only sell it to you if you have one."

"Oh. Well what is it?"

The man bent down and pulled an item from behind the counter. Inside of a small bag was a sole potato chip.

Natsu quirked a brow, crossing his arms. "A chip? You're selling me a chip?"

"It's not just any kind of chip," the clerk said. "It's one that will make things more fun between you and your partner."

"More fun? How?"

"You'll have to see for yourself." The man's lips curled into a small smile, his cheeks tinted pink.

Natsu stared at the chip skeptically. It was a hefty price to pay for just a chip, but the guy did say it'd make things more fun. That was worth it, right? And since the shop didn't sell any celestial keys, they could use the money they saved for that on this instead.

"Alright, I'll take it!" Natsu exclaimed with an eager grin.

The man mirrored his expression, accepting the money and offering him the chip.

Little did Natsu know at the time that the kind of fun the man meant was something totally different.

Arriving at the guild, Natsu's eyes immediately searched for a head of golden hair while Happy flew towards Charle. Finding the blonde sitting at the bar with Cana and Mira, the boy decided to sneak up on her. Right behind her, he squeezed her sides and shouted, eliciting a scream from the girl.

Lucy turned around, glaring at Natsu. "Natsu! Don't do that, you jerk!"

The boy cackled. "It's too funny, Luce!"

"It's not funny!"

"Yeah it is!"

"It kinda is," Cana agreed.

"Yep!" Mira chimed in.

Lucy rolled her eyes. "Whatever." Turning towards her partner, she smiled at him. "How did the job go?"

"Piece of cake!" Natsu answered with a wide grin.

"That's good. I was actually going to go back to my place to write on my novel."

"Oh, I'll go with you."

"Okay, but you need to be quiet since I need to concentrate on my story! Are you going to bring Happy?"

"Nah, he's been talkin' this whole time about winning Charle's heart the moment we got back so I'm gonna let him do his thing."

With that, they were saying their goodbyes to everyone in the guild before heading back to Lucy's apartment. Natsu walked a step behind Lucy as she walked on the edge of the canal. He was on his toes to make sure that she wouldn't fall in- though, that'd be a pretty funny sight. He told her all about their job, all the while watching Lucy.

The sunlight reflected off of Lucy's golden hair, making her look like an angel. His eyes glazed over her curves, his fingers itching to feel them. He shook his head, forcing his gaze onto the pavement.

He and Lucy weren't like that. At least, not yet. Ever since the battle with Zeref and Acnologia, the two were in a weird stalemate. Natsu had a feeling that she had a thing for him, just as he did for her, but neither of them chose to really act on it. Maybe they were waiting for each other to make a move. Natsu wasn't sure. But he didn't want to do anything that Lucy wasn't ready for.

Reaching the girl's apartment, Lucy immediately went to her desk while Natsu situated himself on her bed. They were in a content silence as Lucy worked on her novel and Natsu played with his fire.

Still, Natsu could only keep himself entertained for so long. After half an hour passed of them sitting in silence, he was starting to feel fidgety. No longer interested in playing with fire, he shoved his hands in his pockets, his brows quirking as he felt a plastic bag in one of them. He had forgotten all about the chip.

"Lucy!" he suddenly called out, causing the girl to jump in her seat.

With a hand over her chest to calm her startled heart, she turned to face him. "What, Natsu? Don't just scream my name like that! You scared me!"

He smiled sheepishly, rubbing the back of his head. "Sorry, sorry! But I just remembered something I bought for us!"

This piqued the blonde's interest. In seconds, she was getting up from her chair and sitting by him on the bed.

"What is it?" she asked, a wide smile stretched over her face. Reaching into his pocket, Natsu pulled out the plastic bag, showing it off. Lucy peered curiously at it, blanching when she saw what was inside. "A chip? You got us a chip? Not even a full bag, but just one single chip?"

"Yeah! The guy said that it would make things fun!" Natsu replied.

"How?"

"He said I'd have to see for myself."

Lucy placed a hand on his shoulder, shaking her head. "I'm sorry, Natsu, but you totally got ripped off. The guy just put a potato chip in the bag and said some nonsense about it so some idiot would buy it."

"Oi! I'm not an idiot!"

"You just bought a single potato chip."

"For us," Natsu said, nudging the girl. "I don't think he was lying!"

"What makes you say that?" Lucy asked.

"Because he knew I was a dragon slayer! So this only works for dragon slayers. And he said he could only sell it to me if I have a partner."

"Partner?"

"Yeah. Like you and Happy."

Lucy sighed. "Well, I'll let you have it."

Natsu inspected the chip. It did look like an ordinary chip… He shook his head. He refused to believe that he was played!

So, without a second thought, he plopped the chip into his mouth and began to chew. It tasted like any other chip. Swallowing, he waited for anything to happen.

"Well?" Lucy asked, staring at the boy. "Anything happen?"

The boy crossed his arms with a pout. "Not yet. But just give it some time! I'm sure it'll-!"

Natsu's eyes widened, his jaw slacking. His breaths began to stagger and his heart felt like it was beating a mile per second. He clutched his chest, the world around him starting to spin.

"Natsu?" Lucy called out. "Natsu, what's wrong?"

The boy couldn't even hear her. A strange, foreign heat traveled through his body. Being a fire dragon slayer who ate fire on a daily basis, his body always felt warm. But this was different. This was painful.

Natsu inhaled sharply, fisting his hair as the heat got worse. It felt like it was bundling up, about to explode within him.

Lucy was getting worried. Was the chip poisoned? Was that why he was acting like this? Looping an arm underneath Natsu, she began to lead him towards the door.

"I'm going to take you to the guild!" she told him, unsure if he could even hear her. He didn't react at all, so she doubted he could. "Maybe Wendy or Master can do something about this!"

It was a long, hard walk to the guild. Carrying Natsu the entire way was a struggle. It didn't help that the townspeople were staring at them, and it especially didn't help when Natsu would start to thrash around in pain.

But finally, they reached the guild. Kicking open the door, everyone in the guild turned their attention towards them.

"Someone help me!" Lucy shouted. Carrying Natsu the entire way had taken its toll on her body and she was exhausted. Falling to her knees, she was relieved when Gray and Erza came to help.

"What's wrong?" Gray asked, lifting Natsu and sitting him down at the nearest table. Everyone in the guild circled around them, concerned for the dragon slayer.

"I-I don't know!" Lucy answered, standing right beside the ice-make mage. "He bought some chip from someone saying that it would make things fun or something and next thing I knew he was like this! Wendy, can you help him?"

The girl frowned, shaking her head. "I'm not really sure what the problem is."

"It isn't poison?"

"No. If it were, I could heal him."

"I know where the shop is!" Happy chimed in. "Maybe we should go see the guy that sold it to us!"

"That's a good idea," Erza replied. "It doesn't help that none of us knows what's happening. We need to get some answers."

Lucy frowned, gnawing on her lower lip as she watched Natsu writhe in agony. She hated seeing him hurt. Suddenly, a cold hand landed on her shoulder. Gray smiled at her.

"Don't worry, Lucy," he said. "We'll figure it out. Flame Brains will be back to his annoying, idiotic self in no time."

Lucy nodded, forcing a smile to her face. "You're right. Thank you, Gr-!"

A low growl had interrupted her. Whipping her head towards Natsu, Lucy's eyes grew wide as her jaw dropped on its hinges. Natsu's pupils had turned to slits as he glared at Gray. Anger gleamed in his eyes. Suddenly, scales started to grow out of some parts of his face.

"Dragon Force?" Gajeel asked. "Why the hell is he goin' into Dragon Force?"

Before anyone could say anything else, Natsu leapt from his spot, tackling Gray down to the ground.

"Oi! What the hell, Natsu!" Gray shouted, trying to get him off.

Natsu ignored him, baring his sharp teeth. Another low growl resonated in his throat.

"Don't. Touch. Her," he ground out.

Everyone's eyes widened.

"Wait, is he talking about Lucy?" Erza asked.

"I only put my hand on her shoulder!" Gray said.

This only caused Natsu to get angrier. His nails turned to sharp claws, which he held dangerously close to Gray's face.

"Don't touch her!" he repeated. His voice was lower than normal, scratchy and hoarse.

Erza went to get Natsu off of Gray when the boy threatened to slash at her instead. Lucy swallowed thickly, taking a step towards him. She didn't want to set him off, but she needed to get him away from Gray.

"Natsu," she called out. This gained the boy's attention. "Come here."

He got up and went by the girl's side. Gray scoffed, glaring at him.

"I think I know what the problem is," Levy said, gaining everyone's attention. "Natsu wasn't poisoned. But he was definitely given something."

"What is it?" Lucy asked.

Levy blushed and chuckled awkwardly. "Well, it's going to sound crazy…"

"Just tell us!"

"I think the chip might've been infused with a potion that makes someone possessive and territorial. And since Natsu's a dragon slayer, that side of him is worse than most people's. His senses will be heightened."

"The guy did say that it was meant for dragon slayers," Happy informed her. "And that he could only sell it if Natsu had a partner."

"Partner? Well, that only proves my point. He meant partner as in significant other, not a partner you go on jobs with."

Lucy flushed from head to toe. "Wait… So you're saying that Natsu is possessive of… me?"

"Yep," Levy answered with a nod.

"But-But we aren't even- What!?"

"Oh please," Gray said, crossing his arms. "Everyone knows how you guys feel about each other. And I guess this means that Ash for Brains does too."

Lucy's cheeks were set ablaze. She did not come here to have her feelings towards Natsu talked about amongst the whole guild.

"Don't worry, Lucy," Levy said. "The effect will wear off eventually. For now, just endure it."

"You should probably take him home," Erza suggested. "We don't want him hurting anyone."

Lucy nodded, her heart thumping within her chest. Take Natsu home? While he was like this?

"Okay," she said. "Let's go, Natsu. Happy." That seemed to trigger the dragon slayer as he glared at Happy with a growl. "Seriously? You're getting jealous over Happy too?"

The exceed frowned. "It's okay, Lucy. I'll just go home. You can take Natsu to your apartment."

Lucy smiled apologetically towards the cat, knowing that his feelings were probably hurt. "Alright. Bye, everyone."

The guild wished her luck, and with that, she was out the door.

Even though carrying Natsu to the guild was tough, this was worse. Every time someone so much as looked at her, Natsu was charging them and getting in their faces. The same happened if someone was just walking close to her.

"Stop it already!" Lucy demanded, dragging Natsu by the scarf into her apartment. Once she closed the door behind her, she leaned against it with a sigh of relief, glad to be back home. Since they were alone, there was nobody Natsu could get angry at.

"Well, Natsu?" Lucy started, opening her eyes to glance at him. "What do you want to do-!"

The words died in her throat as she saw the way Natsu was looking at her. She was no fool. She was not blind to the hunger and desire that filled his onyx orbs.

A blush crawled up her face. "Umm, what do you want to do?"

Natsu ignored her and continued to stare at her. Her eyes trailed over the scales that protruded his skin. The dark look in his eyes paired with those scales…

Heat erupted within the girl like a volcano as the area between her thighs began to tingle in excitement. Lucy wanted to bash her own head in the wall. What was she getting turned on for? It wasn't like she could actually do anything!

Still, Lucy blushed from the intense look Natsu was giving her. This was her first time seeing him in Dragon Force. She'd seen him angry many times, but this was different. Though he was angry at everyone else, he never looked angry when he gazed at her.

Lucy was drawn from her thoughts as she saw Natsu walking towards her. With a tiny squeal, she pushed herself against the door. Natsu stopped right in front of her, his eyes boring into hers.

"N-Natsu?" she called out.

Before she could even register what was happening, Lucy found herself caged between Natsu's arms.

"Lucy…" he said, his voice low and alluring. The girl couldn't help but shudder from his voice.

"W-What are you doing?"

Natsu slowly started to lean his face towards hers. Lucy got the hint immediately, squirming in her spot with flared cheeks. Was this really happening? Was this going to be her first kiss?

With a frown, Lucy stopped him.

She wanted to kiss him, she really did. She had wanted to for a long time, actually. After all, she was madly in love with Natsu. But this was different. Natsu wasn't in control of himself and she didn't want to take advantage of him like that.

"I can't," she whispered.

"Why not?" he asked, gently grabbing her wrist.

"Because you may want this now, but I don't want you to regret it when the effects of that potion wear off."

Natsu tugged on her wrist, pulling her against him. "I won't regret it. I'm still me, Luce." With that, he began his descent towards her lips once again.

Lucy's breaths were shaky as he got closer and closer. Her brain was short-circuiting, her thoughts a jumbled mess. She could feel his breath fanning against her face. She closed her eyes, anticipating what was to come. And finally, their lips met.

At first, the kiss was soft, as if their lips were barely even touching. Fire shot through Lucy's body, coursing through her veins. Then, Natsu began to push harder against her, molding his lips with her own.

It was sloppy at first, but they soon got the hang of it, their lips washing over each other's like waves. Lucy, unsure of what to do with her arms, snaked them around Natsu's neck, bringing herself against him. She could faintly hear another one of his low growls, which she took as a sign that he liked it.

Everything was happening so fast. Not even an hour ago, the two were dancing around their feelings. And now, they were sharing passionate kisses.

Lucy couldn't complain about that.

Natsu began to tug on Lucy's lip with his sharpened teeth, gently enough so that it wouldn't hurt her. The sensation was odd, but Lucy found herself liking it as she began to tug on his hair. This spurred the boy to advance further, his tongue darting into Lucy's mouth and sliding against her own.

Lucy's eyes opened as she squealed, unfamiliar with such a feeling. Well, she was unfamiliar with all of this, but that caught her off guard.

Natsu smirked at her, making her fidget in her spot. The way his eyes bore into hers, the teasing smirk…

Natsu leaned towards her again, planting his lips against hers. As if warming her up to it, he switched between licking her lower lip and tugging it with his teeth. Then, he slowly pushed his tongue into her mouth.

Lucy leaned into the kiss, enjoying the odd sensation of brushing tongues with Natsu. His hands landed on her hips, tugging at her flesh that was revealed by her crop top. She could feel his fingers dipping underneath the hem of her shirt. The tingling sensation between her legs grew to a dull ache.

Natsu pulled away from their kiss and stared into Lucy's eyes as he paused his advances, silently asking for permission. Lucy was glad that even under the effects of the potion, he still had to control to make sure she was okay with it. With blushing cheeks, Lucy grabbed Natsu's hand and trailed it upwards, giving him the answer he was looking for.

Natsu crashed his lips over hers once again, his hand slowly moving up her side and under her shirt. His other hand was kept on her lower back, pushing her against him.

As Lucy felt Natsu's hand getting closer and closer to her breast, she couldn't help but squirm in anticipation. He'd touched them before, but this time would be different. She could tell he was teasing her by how slowly he was moving. His touches were driving her crazy.

Finally, his hand grazed her breast, causing her to inhale sharply. Natsu continued his pursuit until his thumb was right next to her hardened nub. He pushed his tongue into her mouth again as his thumb rolled over her peak, eliciting a whimper from the girl.

In seconds, Lucy found herself pushed against the door, moaning as Natsu continued to fondle her breast. To think that she'd been missing out on such pleasure! She could tell that her moans were having an affect on Natsu with the way he started to get rougher with his kisses.'

Not that she'd minded.

Natsu growled again as Lucy's fingers raked his back. His lips left hers in pursuit of her neck instead. He ravaged the skin, sucking it roughly and smoothing his tongue over it, leaving red marks in his wake.

Lucy whimpered again as Natsu's thumb rolled over her nipple. The ache between her legs was growing harder and harder to ignore. She needed to relieve herself. Her body acted on its own as she rolled her hips against Natsu, feeling something hard against her thigh. With flushed cheeks, Lucy glanced down to find something bulging under Natsu's pants.

Natsu growled at Lucy, his body reacting to the way she rolled against him. He suddenly picked her up, all the while sucking on her neck. Her legs wrapped around his torso until she was dropped onto the bed.

Natsu grabbed the hem of her skirt before meeting Lucy's gaze again. She nodded quickly, watching as he tore her skirt off. At this point, she was fine with him doing anything to her as long as he'd relieve her of the ache between her legs. Natsu then ripped her shirt off, literally. Lucy couldn't care less at the moment though. Now she was left in only her red, lacy underwear.

Lucy wriggled in anticipation, waiting for Natsu to touch her again. Instead, she watched as Natsu went to her desk, grabbing one of her ribbons. With an arched brow, she watched Natsu approach her again.

Natsu settled himself over her, crashing her lips against hers. Her hands fisted his hair, but not for long before he grabbed her wrists and held her arms above her head. In seconds, she found her arms tied above her head to the pillars of the bed.

"N-Natsu?" she called out breathily.

The boy ignored her, tracing his fingers over her chest, circling her breasts. Lucy wriggled from the touch and rolled her hips towards him as he grazed her hardened peaks. Natsu smirked, amused with the reaction. And now Lucy had figured out why he had tied her up.

To torture her.

Instead of finishing her like she had hoped he would do, Natsu took his time teasing her. His lips traveled from her own lips towards her neck, then towards her chest. She swallowed thickly as he left butterfly kisses over her collarbone and down to the crease of her breasts. He circled the area around her sensitive nubs before slowly grazing his tongue over them.

This elicited a loud moan from Lucy, rolling her hips in need of being relieved. Natsu pulled the nub into his mouth, sucking and licking it. Lucy felt like she was walking on air, like she was on ecstasy. She'd never felt anything so pleasurable before, it was driving her crazy.

"N-Natsu…" she breathed out, her face flushed and dotted with sweat.

"Not yet," he replied, moving his face to her other breast and repeating the process. Lucy wasn't sure how much longer she could hold up.

Soon enough, Natsu's hand slid up her thigh, towards her underwear. His fingers danced along the hem, teasing her by sometimes slipping a finger underneath.

"Natsu," Lucy said, glaring at him.

"Beg for it," Natsu demanded.

"I'm not going to beg!"

Natsu's finger grazed over her underwear, feeling her juices soak through the fabric. His fingers delved closer and closer to her entrance, making her moan. Finally, she was going to be relieved of this suffering!

Then Natsu pulled his hand back, smirking at her.

"Beg," he said.

"F-Fine!" Lucy shouted, no longer able to control herself. "Please, Natsu. Please, for the love of god, finish what you started."

Natsu grinned, showing off his sharp teeth. Instead of using his fingers, which was what Lucy expected him to use, Natsu left kisses starting from her breasts, trailing down her stomach and over her underwear. Using his teeth, he tore the underwear apart, reveling in the flesh that he'd never seen up close like this before.

"N-Natsu?" Lucy called out. "What are you doing?"

He ignored her as spread her legs farther apart and began kissing her inner thigh. He slowly moved upwards to her folds.

Lucy's eyes widened as she realized what he was going to do. She squirmed, unable to hold still as his lips worked their way up to her region. Finally, he hovered over her folds, his hot breath fanning her entrance. Then, he began to suck on her lips, causing Lucy to moan.

He flicked his tongue over her clitoris, amused with the reaction as Lucy arched her back and screamed his name. He did it again and again, teasing her before he slid his tongue past her folds and circled her entrance. He could feel Lucy's legs wrap around his head, but he grabbed them and pushed her legs as far apart as he could, keeping them in place no matter how much she wriggled around.

And once his tongue slowly entered her, she began to thrash around.

"Natsu!" she cried, unable to help herself. The area was so sensitive, she needed to wrap her legs around his head, but he wouldn't let her. No, instead, he kept going deeper inside of her, exploring her edges with his tongue.

Lucy could feel her toes curling as she was on the brink of release. Once Natsu quickened his pace, her legs buckled and she shattered against him, calling out his name. It was like she was on a high, her body trembling as pleasure washed over her. Moans continuously slipped past her lips as he continued to circle his tongue inside of her even though she already climaxed. She rolled her hips against his face, trying to get his tongue even deeper inside of her.

Once the waves of pleasure began to die down, Lucy's legs went limp and Natsu finally pulled his tongue out of her. His eyes trailed over her naked body, dark and hungry still.

"Want to untie me now so I can finish you?" Lucy asked between pants.

Natsu smirked, shaking his head.

"Nah, I'm gonna keep you tied up."

"How am I supposed to finish you then?"

Natsu brought a finger to her mouth, answering her question with the action. Lucy's blush deepened as she nodded her head. She couldn't help but agree to whatever Natsu wanted. Honestly, she wanted to do it too.

So, she watched as Natsu pulled down his pants, his hardened member finally being set free. He caged Lucy between his legs as he brought his cock up to her mouth. Lucy opened her mouth, allowing Natsu to push his shaft inside.

Lucy was a little embarrassed to be in such a position, but at the same time it was exhilarating. Now she knew how Natsu had felt while pleasuring her. She enjoyed being able to pleasure Natsu.

He slowly pushed deeper inside, as far as he could before Lucy's gag reflex would be triggered. Once he knew how far he could go, he picked up speed, thrusting in and out of her mouth. The warmth of her mouth over his length had him seeing stars.

It didn't take long for him to feel like he was about to finish, not when Lucy tightened her lips around his shaft so that it tugged at it every time he thrusted. He could tell she was feeling adventurous herself.

Natsu's legs buckled and he moaned softly as he pulled out immediately, white liquid spurting out and landing on Lucy's face. His breaths were staggered as he leaned over her, watching the liquid drip down the side of her face.

Lucy's eyes widened, feeling a warm liquid slide down her face. She knew what it was, and honestly she was a little thrown off for a second. She'd heard Cana share stories of guys finishing on her face, but it never sounded appealing to her. But now, watching Natsu's eyes glaze over the trail of cum on her face in satisfaction, she began to understand why some girls liked it.

Natsu tore the ribbon that he had used to keep Lucy tied up. Her arms fell limply at her sides, numb. The two of them laid side by side, silent, save for their panting.

"How was it?" Lucy finally asked.

Natsu smirked at her. "Let me put it this way, you better relax while you can before we go for another round. And don't even bother putting on clothes unless you want me to rip those off too."

Lucy grinned, a blush spreading over her face. Suddenly, Natsu's words from before replayed in her head.

"The guy said that it would make things fun!" Natsu had said while explaining why he bought the chip.

Well, the guy wasn't wrong.

That was definitely fun.

AN: Lmao this is the dirtiest thing I've ever written i'm honestly a little embarrassed I can't stop laughing hahaha.