Author's note: This is partially inspired by my room mate's cat Quincy, who has an unholy affection for coffee.
Also... my husband has done this.
The dragon slayers all had better than average senses.
Oh, it was exaggerated to some degree. Natsu could no more sniff out the scent of a bandit from a hundred miles than Gajeel could hear a conversation two buildings away or Wendy could see individual microbes on a sick patient. But all of them were endowed with above average sight, hearing, and smell, at the expense of a certain normal human sense of taste (Natsu's fire tasted like cotton candy to him, and Gajeel's iron apparently tasted like bread. And Wendy once admitted that she could taste flavors in the air, after which people always felt bad about cutting wind around her.)
So it was that Natsu knew every single time Lucy switched any of her bath products.
She was seasonable about her lotions and soaps, and haphazard about her shampoo and conditioner. She switched brands of deodorant every time one ran out (perhaps never really satisfied with any of them.) At some point, she'd traded in her lavender scented body powder for a more sporty scent. She wore little makeup - it was not really her style - and she eschewed traditional perfumes in favor of lighter body sprays, something Natsu's nose appreciated greatly.
One day, she came into the guild after one of her seasonal switches. Gone was the soft spring scent of melons and cherry blossoms. In its place was a much sharper, brighter scent that made her smell like she'd just stepped out of the shower with every movement.
Natsu was intoxicated.
While they were sitting around a table, having a discussion about upcoming mission plans with Erza and Gray, Natsu found himself leaning in closer and closer to her, until he was sort of awkwardly leaning back behind her, inches from her hair. He inhaled deeply.
"Natsu," Erza said sharply once she noticed him, and he sat right back up at her warning look, "there is a mission on the board that seems tailor made for you and Happy. They need a large quantity of trash burned up in Lupine." Erza flicked the paper toward him. "You may want to team up with Juvia to ensure that the destruction doesn't go too far."
Gray opened his mouth to object - whether it was because ice would do just as well, because Natsu would still manage to burn down the entire city regardless, or because he didn't want Juvia to leave without him - but Natsu spoke up first.
"Naw, Lucy can come for that, as long as she can use Aquarius," he said, unwilling to be parted with the fabulous smell emanating from her body.
"Well, if we take the train we can be there in a day, and I have access to her for the next three days," Lucy agreed after a few moments of mentally calculating on her fingers.
All thoughts of Lucy's wonderful wonderful smell abandoned his mind at the mention of the method of travel they'd need to take.
"Ugh," he said, and she patted him gently on the knee, releasing a fresh wave of the yummy smell and clearing his nausea a tiny bit.
They left for the trip the next day, and for once Natsu's nausea was kept to a minimum, because Lucy had drowned herself in the new summery smell and he lay on her lap, simply breathing. She stroked his hair absently, thinking he was asleep.
He was still trying to pin down the new scent. There were lemons and orange blossoms and maybe some sharp flowers and some notes of ginger. There was also a sugary component, too.
He began to wonder if she tasted even half as fabulous as she smelled.
Hesitantly, he made a show of shifting in his sleep, then quickly slipped out his tongue to "accidentally" dart against her arm. The smell intensified, and she did indeed have a sweetness to her skin. Whatever the scent was she'd switched to, she was definitely using a sugar scrub as part of her routine.
The job was not very high paying - just a hundred thousand jewels total, split three ways - but Lucy, Natsu and Happy had learned that they often had better luck going after smaller jobs they'd have less risk of screwing up than trying for big prizes and accidentally destroying an entire town.
They finished the task within a few hours, turning an old condemned apartment block into ash and mud. Natsu systematically burned, taking care not to spread the fire too fast, while Happy flew overhead with buckets to keep the fire under control. After they were done, a good hosing down by a pissed off Aquarius finished the mission.
They took their pay - 33,000 jewels each - and headed off to the campsite next to a small lake that Natsu had picked out for them earlier. Staying in a hotel would cost too much for such a low paying job. Making a fire to ward off the late spring chill was no problem for Natsu, and before long they'd set everything up and settled down comfortably for the evening.
They ate dinner - fish Happy caught cooked over the open flame, a salad picked from the forest, and crackers they had brought along. They also roasted marshmallows, Natsu naturally eating them whole while they still flamed. Some of the wonderful burnt sugar tasted an awful lot like how Lucy's arm had on the train.
"I'm going to wash up," Lucy announced once they'd cleaned up their dinner things, and grabbed her bag of toiletries. She headed off toward the lake.
After she was out of earshot, Natsu took the opportunity to smell the rest of her traveling gear. Oh gods, the smell was everywhere. He sniffed deeply, resisted the urge to roll around it like he was Happy with a bowl of catnip.
"Natsu~ what are you doing?" Happy asked innocently, but his feline grin was just a hair wider than normal.
"She changed," and here Natsu sniffed desperately, "her bath soap to something new for the summer. I can't help it, it smells so good." Sniiiffff. "It smells better than fire tastes."
He was getting intoxicated by the smell. He fell onto the ground, hugging her duffel bag, inhaling deeply. Happy fell over laughing as he rubbed his face against it.
It was to this bizarre sight some time later that a freshly bathed Lucy returned, wearing the traveling pajamas she preferred when they were outdoors.
"Natsu... what the hell?"
It would have been better if she screamed, but her voice had dropped an octave and she enunciated each word slowly, with emphasis.
Unfortunately for her, she had used the same bath soap... and shampoo... and lotion... and sugar scrub... and body spray... and the faint wafts coming from her luggage were nothing compared to the smell coming straight off her body.
Natsu let go of her luggage and crawled across the ground to her, twitching uncontrollably. She really did shriek this time, and hopped away from him, lifting one leg up as if she was recoiling in horror from the scent-infected zombie that Natsu had become.
"So good," he croaked, and made another effort to reach her across the ground. "You changed your soap..." he tried to explain, even as he was completely drunk on her smell. "It's so good... I can't help myself."
She looked at him, with almost pity in her eyes, as he triumphantly reached her bared ankle and started sucking on the skin above her sandal strap.
"It's B&B White Citrus," she said faintly, clearly trying not to lose her shit over her best friend currently giving her a hickey on her ankle. "I can give you the bottle if you'll stop humping my foot."
She reached into her toiletries bag and pulled out a bottle of lotion, dangling it in front of Natsu's face. He joyfully latched onto the bottle, flipped open the lid, and started sniffing it like it was glue.
Happy was laughing hysterically the entire time.
"It's not funny, cat," Lucy hissed, although her lips twitched nonetheless as Natsu cradled her body lotion like a toy. "Has he ever done this before?"
"Nay," Happy said, in between giggles. "Although he's liked the way you smelled since he met you, he said."
With a sigh she plopped down on her bedroll, setting her chin in her hands. Natsu watched all of this through a daze. The lotion by itself was amazing, but it was missing the layer of Lucy beneath it.
Eventually, he managed to get himself under control. He gave one last final sniff, and then closed the lid, contented.
"Are you quite done?" she asked, still trying not to laugh.
"Yeah," he said sheepishly, and sat upright. "I think I've been smelling it so long now I'm getting used to it."
She raised one delicate eyebrow at him. "I'm glad." She still eyed him suspiciously as he handed her the bottle back. "You'd better not have another attack like that in the middle of the night. I'm not sure I want my luggage assaulted again."
Natsu sighed happily, still riding on the smell-high from the amazing stuff. "I think I'd be more likely to jump you directly," he said, looking at her with a surprisingly tender smile.
She blushed a beet red. "I'll tell Erza on you," she threatened.
Not even the threat of the Titania was enough to break Natsu's stoned-on-citrus mood. "She'll punch me and then collect her ten thousand jewels from Cana," he mumbled, and suddenly unleashed a mighty yawn. He stepped away from her and plopped onto his own bedroll.
"Let's get some sleep," Lucy said warily, eying her partner from across the banked fire.
"Aye," Happy agreed from the end of Natsu's sleeping bag, where he was tucked into his own tiny blanket. "I'll protect you from Natsu, Lucy~" he promised.
"Gnight, Lucy," Natsu said.
Almost a minute of silence passed.
"Can I have the bottle of lotion back?"
She threw it across the banked fire, not caring if she hit him on the head.
When they returned to Magnolia, she made a great show of tossing out all the expensive bottles of lotion and soaps she had just bought a few days ago. It smelled great, but if it turned her partner into a raging lunatic, then it was no good.
Natsu watched all this mournfully, already missing the incredible high he'd gotten from the stuff. He had to resist the urge to dig it out of the trash can and rub the girly smell all over himself.
A quick shopping trip at B&B later, she had an entirely new summer scent, one that was still crisp and clean, but that did not involve orange blossoms or citrus or daisies or anything of the sort.
And when she showered and returned to Fairy Tail the next day, expecting to be totally immune from Smell Zombie Natsu, she was in for a nasty surprise.
"Yo," a mostly naked Gray said, waving from their table, where Juvia was giving him a back massage without him even really noticing. Erza waved with her fork, her mouth stuffed full with chocolate cake. Natsu brightened up when he saw her, but then his joyful expression turned to something akin to shock.
"Lucy?" he said, and she felt her blood run cold when his nose started quivering in the air.
"Yes, Natsu?" she said, taking a step back. Oh no. Oh no no no no.
"Peaches," Natsu called out, identifying the first note in the new smell. "Pineapple. Coconut oil. Verbena."
"Run Lucy!" Happy warned, and she turned to do so quickly, desperately dashing out of the guild with a snorting Natsu following behind her.
Gray and Erza and Juvia all stared at the duo, astonished.
"He likes the way she smells," Happy said, blinking once and grinning widely.
The pair returned to the guild the following day, both looking rather glowing and subdued. Natsu refused to let her out of his smell radius, and judging from the smirks from pretty much everyone in the guild, it was clear what events had transpired after Natsu had caught her the day before.
Cana cursed and handed Erza ten thousand jewels.
And then, everyone noticed the way Gajeel was suddenly eyeing, or rather, sniffing at Levy, who had unknowingly donned good ol' B&B White Citrus for her summer scent.