Normally, Lucy Heartfilia wasn't one to get all excited about training. But today was different! Recently, after her battle with a mind-controlled Juvia at the Tower of Heaven (alongside a few other locations), it became apparent to Lucy that without her spirits, her offensive power was really lacking, even with her signature whip. And while she loved her celestial spirits and trusted them with her life, she had to admit she had become overly reliant on them for fighting.

So Lucy had spent the last week researching, trying to see if there were any spells that would synergize with her Celestial Magic. And lo and behold, one trip to the guild library ended up with finding an old tome called 'Celestial Power.' However, the book was also a few centuries old and was in quite a decrepit state. More than 80% of the spells and writing were eligible. And that was without considering that the book also happened to be written in an ancient language.

But thanks to some help from Levy, Lucy was able to somewhat translate one spell: Cosmic Might! Supposedly, from what Levy could translate, it was an enhancement spell that channeled a Celestial Wizard's inner cosmic power, granting them a triplicate boost to their strength, stamina, and durability. Now that was the kind of power Lucy was looking for!

So today, the blonde Fairy Tail mage found a secluded spot in the woods near Magnolia, ready to test out her new spell. In said spot was a rock about as tall as Lucy herself, and almost wide enough to be considered a boulder. Lucy tried to lift it up, but the massive rock refused to move.

'Okay, that's really heavy.' Lucy thought, deciding to use moving the rock as a test of Cosmic Might's power boost. She placed the book with Levy's translated notes inside on another rock, ready to try out the spell.

'First; focus on the mana within you.' Lucy thought, following the instructions. 'Imagine it like a swirling galaxy inside you. Then, imagine that galaxy expanding throughout your whole body.'

She did so, and felt the familiar jolt of her own mana. The same mana she felt whenever she summoned a spirit, going into her arms, legs, and the rest of her. She could feel it. Now, she just needed to say the chant to activate the spell.

"O Mighty Stars shining through the galaxy, grant this vessel the power of a raging supernova! COSMIC MIGHT!"

In an instant, Lucy felt a surge of power flowing through her! Her body shined with the light of the cosmos…for less than ten seconds. The blonde blinked, looking down at herself.

'Is…is that it?' She mentality asked herself, clenching her hands. Lucy didn't feel that much different than usual. But she figured that maybe it was just a quick-acting spell. So she decided to test it by moving the big rock.

It…didn't go so well.

"Come on!" Lucy shouted in frustration. The rock was just as heavy as before. She strained her arms and legs like crazy as she tried to move the rock. But after groaning and sweating for a bit, Lucy managed to slide the rock forward…by about an inch.

"Dammit!" Thoroughly exhausted, Lucy laid down on the grass. She was both disappointed and frustrated. Something must've gone wrong. Maybe she and Levy mistranslated the text. Maybe she did the spell wrong. 'But how am I supposed to know what I did wrong? It's not like I can ask the guy who made the damn thing!'

Lucy lay there for a minute contemplating…but then, an idea came to her. She couldn't ask the author the tome…but she could ask someone who probably knew a thing or two about it! Lucy stood back up, grabbing a certain silver key.

"Open, Gate of the Southern Cross - Crux!"

In an instant, the floating, living cross was before the blonde. "Afternoon, Ms. Lucy."

"Hey, Gramps." Lucy said, explaining her current predicament, even showing him the tome with Levy's translation notes. Crux studied both the tone, as well as the spell somewhat active within Lucy.

"Well, the translation is on point. And from all accounts, you cast the spell correctly."

"Really? But does it feel so weak?"

"Ah! That's where you and that friend of yours mistranslated it. You see, the spell does triple the caster's physical attributes…but how effective the triplicate boost is lies solely on the caster's pre-existing strength and physical fitness."

And that's when everything made sense to Lucy. She was proud of how pretty and curvy she was…but the blonde was completely lacking in terms of fitness! Just running for too long made her winded.

No wonder the spell barely worked. A triplicate physical boost on someone with zero physical might…was still zero!

"Aw, nuts."

Later that evening, Lucy was at the guildhall, her head slumped against the bar. Levy, Mirajane, Natsu and Happy were around her, feeling a bit of pity as she explained her current predicament.

"Well, that sucks." Natsu said, blunt as ever.

"Aye. If only the spell could turn your booby fat into power." Happy said. "You'd be unstoppable, Lucy!"

On the one hand, Lucy was annoyed at the cat calling her fat. On the other hand, he complimented her gifted rack. And on the other, other hand, she was still depressed that her spell didn't work, so she didn't even bother retorting.

"So what are you going to do, Lucy?" Levy asked.

"I mean, it's obvious!" Natsu said, holding his fist up. "Ya gotta get into shape!"

"But I don't know the first thing about physical training!" Lucy cried out. "I mean, unless you know anything about it, Natsu."

The dragon slayer thought about it…and realized he wasn't a guru when it came to getting fit. His toned body was mostly the result of his combat and magic training. And even Natsu was self-aware enough to realize he probably wouldn't be good at teaching anyone anything. "Sorry, Lucy."

The blonde slumped even more against the bar. Mirajane felt bad for her friend. The white-haired model thought of how she could cheer Lucy up…but then she saw Elfman walk into the guildhall, and an idea popped into her head.

"Elfman! Over here!"

"Hey, Mira!" The large, muscular man said as he approached the bar. "What's going on?"

"Well, Lucy's got a bit of a problem."

One explanation later…

"So, do you think you can help me?" Lucy asked Elfman. The white-haired man thought about it for a moment before smirking.

"Just leave it to me, Lucy!" Elfman proclaimed. "With my training, you'll become a real man and use that spell to its full power!"

Lucy wished he left out the 'real man' part, but she really appreciated the help regardless, standing up and shaking Elfman's much larger hand. "Sounds like a plan!"

"Excellent! We'll start tomorrow! Just be sure to be ready bright and early. Oh, and wear some old clothes that you don't mind getting a sweat on!"

"Right!" Lucy said with excitement. If this worked, Cosmic Might would let her become a powerhouse alongside her spirits and her friends! She was all amped up.

But the next morning, that excitement turned into grogginess. Lucy heard a loud knocking at her apartment door. "Hang on." Lucy yawned, slowly walking to the door. She opened it and saw Elfman, standing there in a dark purple tracksuit. "Elfman?" Lucy looked outside and saw that the sun wasn't even out. "What time is it?"

"6:15. Bright and early, just as promised." The Beast Take-Over mage said with his usual gusto.

"But it's not even bright out." The blonde grumbled and sighed. "Just…just give me a minute to change."

"Make it quick! We're starting off with some light jogging around Magnolia Park!"

"R-Right." Lucy said, changing into an old t-shirt, sweatpants, and sneakers. But about an hour later, the celestial mage would realize she would need to buy a vital piece of clothing after some flopping and unfortunate chafing.

She would need to buy some sports bras.

The following week was one of the most grueling weeks in Lucy's young life, and really hammered in just how out of shape she was. And it also taught her that there was more thought that muscle heads like Elfman put into their routine than one might think.

First off, there was a difference between muscle building and stamina training. Elfman explained that stronger muscles didn't automatically translate to more stamina, which was arguably more important in a tense wizard fight. Lucy had never jogged that much in her life, and got winded after barely running two miles.

Second, when it came to building stronger muscles, it was a bad idea to try and work on every muscle group at once. Each particular muscle needed a dedicated day to work on, so that only that muscle group would be sore the next day. The soreness Lucy felt in her arms after trying to do a rep of bicep curls was unlike any pain she had felt before.

Third, the 'dieting'. Lucy saw Elfman put away a ton of chicken for lunch, and realized that was a normal thing for him. Lucy's stomach definitely wasn't agreeing with the sudden intake of more protein-enriched food. Elfman had also told Lucy to try avoiding or at least not eating as much fatty foods. Which meant having to cut back on the chocolate (and she had just learned a new chocolate chip recipe too.)

By the end of the week, Lucy flopped onto the grass of Magnolia Park, her body and clothes soaked in sweat, her limbs sore and her breath hitched. "Elfman…can we take a break?"

"Sure, thing. It ain't manly to overexert yourself." The white-haired man said as he handed Lucy a water bottle, which she readily excepted. After taking a big gulp of the water, Lucy sighed.

"I'm really pathetic, aren't I?" Lucy said, confusing her training partner.

"What makes you say that?"

"I'm a mess. I feel like my entire body's about to give out after a week, and you don't even seemed phased by all this."

"Well, that's because I've been doing this kind of training for years." Elfman said. "And you've only just started."

But he saw that Lucy was still a bit disheartened. So he continued. "Mira showed you what I used to look like when I was a kid, right?"

Lucy nodded. It was still hard to believe that the mountain of a man was ever a scared and nervous child.

"Well, I didn't become the man I am overnight. I wanted to become more than just a coward that relied on his sisters. But the path to getting stronger was grueling." Elfman said, his eyes giving off a hint of nostalgia. "There were days where I felt like my limbs would fall off, and I just wanted to call it quits. But I kept telling myself, 'Come on, Elfman! You need to become a man strong enough to fight and protect those close to you! Don't you dare give up!' It look months and months, but I eventually got used to the training. And now, I can't imagine myself any other way. And yes, I might not have always succeeded…" He said, his eyes taking on a sad look as he remembered Lisanna. "...but I'm always aiming to improve myself day by day."

He then stood over Lucy, a confident smile on his face. "So don't beat yourself up, Lucy. You only just started trying to train and get stronger. It might take awhile for the results to show, but eventually, it will get easier. And I swear, you will get stronger. You just need to keep pushing forward like a real man!"

Lucy looked up at Elfman, and began to see him in a new light. She had figured Elfman was just a big guy obsessed with manliness. But behind all that bravado was a man with amazing determination and an aim for self-improvement. And it was that aim that reminded Lucy why she was doing this.

She wanted Cosmic Might to work! She wanted to be strong enough to stand alongside her spirits and her friends as an equal! To be worthy of being called a Fairy Tail mage!

"You're right! I'm gonna keep at it and get stronger! Like a real Fairy Tail wizard!" Lucy proclaimed, standing up with renewed determination.

"That's the spirit!" Elfman shouted, the two going right back to their jog.

And for the next two months between jobs and working on her novel, Lucy continued her physical training alongside Elfman. In that time, the tall Take-Over mage had become a staple in her life alongside Natsu and the others. She could now consider him a close friend.

The results of her training were also starting to show. Her body was way more toned, with the light bit of fat that used to be around her stomach now gone. And as a plus, the lower back pain she had to deal with thanks to her plentiful bosom was way less of a pain to deal with, due to her back now being firmer as well.

But today was the day when Lucy would try out Cosmic Might once more, returning to the same clearing in the woods with the large rock.

"Alright. Here we go!" Lucy began to channel her magic. "O Mighty Stars shining through the galaxy, grant this vessel the power of a raging supernova! COSMIC MIGHT!"

Once again, Lucy felt a surge of magical energy flow into her body. It felt stronger than the first time she used it as her body shined once more. But strangely, Lucy also felt a strain on her body, like something was tugging at her skin. The blonde looked down, and her eyes widened when she saw that her body was starting to become more muscular!

Biceps began to form on her arms! Her shoulder grew broader! The fat on her thighs and calves turned into a muscle as well. Lucy could also feel her stomach tightening, a pair of abs forming. Her back muscles becoming more pronounced. And even a pair of pecs forming behind her boobs. And speaking of her breasts, she could feel them becoming slightly firmer as well.

After less than a minute, the spell-casting ended, and Lucy was left stunned at the state of her body. 'Muscles.' She thought, holding her arm up. Out of curiosity, the Celestial Mage flexed her arm, and her bicep bulged, forming a little mountain of pumped feminine flesh. 'I actually have muscles. Can't say I was expecting that.'

However, Lucy decided to worry about how her body looked later. Right now, she had to test to see if Cosmic Might actually boosted her body now. So Lucy went over to the large rock and grabbed it. With gritted teeth, Lucy started to lift, veins appearing on her arms and legs as she do her. And to her glee, she could actually lift the rock off the ground!

It was still heavy, but with some effort, Lucy discovered she could hold it over her head for a bit! The now-buff blonde placed the rock down, and decided to test the rest of her abilities.

First, Lucy began to run through the forest and realized that she could run faster than ever. She wasn't anywhere as fast as Jet, but she could definitely outpace Natsu and possibly Erza if she wasn't using her flight armor.

After that, Lucy tested how high she could jump, her thighs bulging before she leaped six feet into the air…and ended up landing face-first into a tree branch.

Finally, Lucy decided to run to the guildhall to test her stamina. And after a few minutes of running, rather than being absolutely tired, Lucy just felt a bit tired.

The blonde smiled as she entered the guildhall, spotting her team hanging out at the bar. "Guys, it worked! Cosmic Might worked!"

"Oh, that's good to-HOLY CRAP, Lucy!" Natsu said as his eyes bulged. "When did you get ripped?!"

"Oh, right." Lucy said, remembering the physical change her body went through. "It looks like when the spell enhances my physical abilities, this is the side effect. Pretty weird, huh?"

"No, that actually makes sense." Gray stated. He was shirtless, which allowed Lucy to compare her muscles to the Ice Mage's. The two were basically equaled in terms of fitness and bulk, but of course, Lucy's body was more curvy and womanly.

Lucy then began to tell her teammates about what she just did the woods. Erza looked proud, Gray and Happy were impressed, and Natsu wanted to spar with Lucy. The blonde was happy to hear all of this, but then her eyes spotted Elfman walking down from the guildhall's second floor, running towards him. "Hey, Elfman!"

The manly mage looked and his eyes blinked at the sight of his training partner. "I guess the spell worked."

"Yup! I'm stronger than ever!" And then, to Elfman's surprise, Lucy wrapped her muscular arms around him and gave him a big hug. She then looked up and smiled at the taller mage. "Thanks for all your help. I couldn't have done this without you."

A light blush appeared on Elfman's face as he took in Lucy's bright smile before giving one of his own and patting her on the head. "I wouldn't be a real man if I didn't help my friend unlock her full potential."

But as the two separated from their embrace, Mirajane gained an excited and mischievous look in her eyes. Lately, her little brother had been talking about how impressive Lucy was, and how he admired her dedication to improving herself. Maybe there weren't any romantic feelings brewing between the two yet, but there was something brewing.

A few hours later, Lucy returned to her apartment, the muscles gained from Cosmic Might vanishing as the spell ran its course. It had taken two hours to do so, but Lucy figured that in a real battle, where her mana would be used to summon her spirits in tandem with Cosmic Might, the duration would probably be a lot shorter.

'I'll have to start planning some combo moves with Loki and the others.' Lucy thought, drying herself off as she stepped out of her bathtub. The blonde looked at her naked body in the mirror, and a curious thought entered her mind. One she decided to act on.

"Cosmic Might!"

Lucy's muscles grew to their previous enlarged size, and now, the buff blonde was able to get a good look at her mystically enhanced body in the nude. She flexed and posed, observing how each muscle group reacted to her movements.

"You know…" Lucy said, looking at herself in the mirror as she did a side chest pose. "…I look pretty good with muscles."

Lucy had prided herself on being pretty and curvy, and had been worried her mystically-added bulk would detract from that. But it didn't. Her body still had an hourglass figure and her girls were still huge. But now, said figure and bosom were enhanced by her muscles.

Lucy began to touch her bicep, and giggled as she felt just how hard and firm it was. Not only could she feel the power of Cosmic Might flowing inside her body, but she could feel it just by feeling herself up.

But then, another thought appeared in Lucy's head.

"This spell made me go from toned to Gray and Natsu-sized. I wonder…if I was just this muscular regularly…would Cosmic Might make me even bulkier?"

To her surprise, Lucy felt a shiver of anticipation within her. The thought of her muscles being even larger made her more excited to keep training.

'Well, that settles it.' Lucy thought as she started getting ready for bed. 'Tomorrow, I'll go even harder with my strength training! Watch out, bad guys! 'Cause the new and improved Lucy's gonna kick all your asses!'

A new chapter of Lucy's life had just begun. Soon, she would crave her own legend alongside her friends at Fairy Tail. But she would also find love in the most unexpected place. And would happen sooner than either Lucy or Elfman would realize.

Well, here's another Female Muscle AU that's been rattling in my brain for a while. I know, Elfman and Lucy do sound like a weird pairing, but I love the thought of these two together.

I also wanted to try my hand at a story where one of the buff beauties can willingly grow bigger. But it's not 100% percent a cheat as Lucy has to keep getting stronger in her base form and actually build bigger muscles in order to get the most out of Cosmic Might.

Of course, we are gonna get some filthy muscular erotica between the Manly Take-Over Mage and the beautiful Celestial Mage in another chapter. And who knows, they might encounter another beefy beauty who wants in on the fun.

Until then, have a safe day!