We find Natsu and Wendy in the mountain ranges on the outskirts of the town of Magnolia where the Fairy Tail Guild Hall and it's member's reside. After recent battles in the Grand Magic Games Wendy decided that she needed to get stronger as a member of Fiore's number one guild, turning to her fellow Dragon Slayer Natsu Dragneel for guidance.
She looked up to the pink haired mage for his mastery of the Dragon Slayer arts, particularly his combat abilities which were so strong he'd managed to beat two other Dragon Slayers at the same time. Naturally, this would be the primary focus of her training with Natsu as the two set off without their Exceed partners.
"Wendy, I hope you're ready for some serious combat training!" Natsu said excitedly, getting pumped up to raise Wendy's skill level and asses her current powers.
"Ye-Yeah, I'm ready!" Wendy confirmed, trying to sound as confident as possible as the two Dragon Slayers got into their respective fighting stances. A gust of wind kicked up dust between the two mages, each wondering who would be the first to declare an attack. Of course, it didn't take a genius to figure out that Natsu would make the first move. He leaped into the air, using the sun as a backdrop to disguise his first attack.
"Fire Dragon Iron Fist!" Natsu declared, coating his fist in flames and thrusting his fist towards Wendy. The young Sky Maiden, not confident in her ability to directly block Natsu's attack took a different approach.
"Oh, swift winds that run the heavens. Vernier!" Wendy chanted, casting an enchantment on herself that would increase her overall speed. Shortly after taking evasive actions to dodge Natsu's strike, his flaming fist meeting with the dirt as Wendy maneuvered around him.
Next, she focused on a counter-attack "I call upon thee, the starward fight to claim the heavens. Arms!" Wendy chanted, adding a strength enhancement on top of her boosted speed to increase the power of her attacks. "Sky Dragon Roar!" She yelled, attacking from Natsu's right side with a massive gust of wind shot from her mouth.
"Fire Dragon Roar!" Natsu yelled, responding to Wendy's counterstrike with his variation of her breath attack. Fire and wind met between the two Dragon Slayers, their magic power duking it out before Natsu's flames overpowered Wendy's magic. Even with her enchantments, there was a clear difference in their abilities.
Wendy moved to dodge, landing off balance and creating an opening for Natsu to attack. He dashed towards the young girl, coating his entire body in flames. Natsu then raised his hands over his head, gathering the fire into a single point. "Fire Dragon Brilliant Flame!" Natsu yelled as he tossed a giant fireball in Wendy's direction.
Wendy froze for a brief moment, thinking she couldn't possibly deflect or repel Natsu's attack. That's when she remembered a third Dragon Slayer Secret Art that Grandeeney had left her along with the Sky Drill and Milky Way. However, she'd never before pulled off the move in her training.
Wendy stood up tall, gathering her magic power she planted her feet firmly at her sides. "Sky Dragon Secret Arts, Act of Compression!" Wendy yelled, creating a massive vortex that swallowed Natsu's magic in seconds. Unfortunately, the giant twister expanded so much that Natsu himself got sucked into the vortex she created. He tried to stand his ground but with nothing to hold onto he was helpless before Wendy's sudden power up.
With Natsu's magic trapped and no knowledge of her friend's predicament, Wendy began controlling the vortex with her hands. Making it smaller and smaller she suffocated Natsu's flame attack, shrinking it down to an ember in moments before it completely disappeared within Wendy's tornado of magic power.
After successfully defending herself Wendy released the spell and the vortex unraveled into thin air. She was so proud of herself, pulling off an advanced technique she didn't even believe possible. She turned to Natsu, looking to thank him for drawing this power out of her. But he was nowhere to be found.
"Natsu, where did you go?" Wendy asked, stepping out into the clearing to look for him. Meanwhile, Natsu sat up rubbing his head after getting caught in Wendy's spell. That's when he noticed strange vibrations traveling through the ground, almost like miniature earthquakes.
On the contrary, they were footsteps. Most likely originating from some giant magical creature like a Wyvern or giant Vulcan. Natsu turned to towards the source of the vibrations, shocked when he saw a giant human's foot land at his side. He instantly recognized the footwear and thought it was impossible, looking up to see a massive Wendy Marvell towering over him.
"Wendy, down here! Wendy!" Natsu yelled, repeating the young girl's name as she looked at her surroundings. She seemed to be confused, reacting to his call for her attention.
"Natsu! Wait, where are you?" She asked, her ears picking up on his voice enhanced by her Dragon Slayer magic. Finally, she looked down, turning her attention on what appeared to be a bug between her sandal-clad feet. "Is that you Natsu?" Wendy asked, shocked by how tiny he'd become. He was barely an inch tall.
"Hey Wendy, how'd you get so big?" Natsu asked, surprised by the young girl's size. Easily dwarfing him at over fifty times his size. Her black thigh high socks alone reached heights taller than the Fairy Tail Guild Hall, leading up to her cotton white panties hidden from the rest of the world under her skirt. Wendy still not realizing that she'd left herself exposed to the bug-sized Natsu.
"What, I'm not taller Natsu. You've shrunk." Wendy clarified, forcing Natsu to observe his surroundings to see that she was right. It wasn't just Wendy, but everything surrounding him was gigantic, absolutely enormous. "Really, but how did this happen?" Natsu asked.
"I'm sorry, it must have been my magic. The spell I used concentrates high force winds to compress magic power and makes it smaller. You must have gotten swept up and shrunk with your attack." Wendy explained sadly, her voice full of regret. Still not understanding how a spell that shrinks magic power could also make a person smaller. Forgetting that on Earthland all living things contain magic.
"Don't worry Wendy. I'm sure somebody can fix this. But first, do you think you can give me a lift back to the guild." Natsu asked, not wanting to walk all the way back to Magnolia.
Wendy cheered up, Natsu was right she thought. Fairy Tail was home to all kinds of powerful mages, surely someone from the guild could reverse what she'd done to him. There was just one small problem.
"Natsu, if you don't mind could we keep this between as few people as possible? I still want to get stronger, but I'm worried that people won't want to train with me if they think I'll accidentally shrink them everytime they spare against me ." Wendy responded, not that it would scare off too many members in Fairy Tail.
"Yeah, sure thing Wendy. Do what you have to, I'd rather not have Erza see me like this anyways." Natsu shivered, the thought of a three hundred foot tall Erza terrifying him. She was already as scary as any monster at her current height.
Wendy giggled nervously, agreeing with Natsu's sentiment. She wouldn't want to end up on the wrong side of a gigantic Erza either. Wendy reached down and picked Natsu up between her fingers, before dropping him into her palm, lifting him to chest level.
~Wow, I can't believe how tiny he is. It almost feels like I'm holding an insect, I better be careful with him.~ Wendy thought to herself as she looked down at Natsu. Then she realized that she didn't exactly have a plan to hide him from her guildmates or the people of Magnolia for that matter.
"Um Natsu, if we're gonna keep you shrinking a secret then I'll have to hide you somewhere. I don't have any pockets n this outfit so I can't guarantee what I have in mind will be very pleasant." Wendy announced nervously, but Natsu was unphased by her words.
"That's fine Wendy! Just take me out as soon as you can." Natsu announced, willingly subjecting himself to being kept wherever the young Sky Maiden choose. Likely somewhere she could feel him constantly moving, so he doesn't accidentally slip out. She didn't want to risk losing him, preparing to deposit him inside her ________ so he can't fall out by mistake.
1. Bra, Wendy takes advantage of her small boobs. Not taking into full account how massive the orbs the flesh might appear to someone of Natsu's current stature. She then walks back towards Magnolia, thinking about what it would be like to have bigger boobs, deciding to take Natsu back to Lucy's Apartment for help.
2. Thigh Highs, Wendy slips Natsu down one of her tight high socks, trapping him inside the fabric while she searches the town of Magnolia for Levy at her usual hangouts such as the library and the park. Hoping her knowledge gather from books can help wendy reverse the effects of the shrinking. Meanwhile, Natsu sinks deeper and deeper down her thigh highs until he falls under Wendy's foot.
3. Panties(back), while it's not her first choice, Wendy admits that it would be easiest to keep Natsu close to her skin, with a lack of better options she drops him down the back of her underwear to feel him against her soft buttcheeks. Meanwhile, she makes the decision to try using her healing magic on Natsu once her magic power recovers.