1

The first thing Tails felt in the morning was an unbearable itch. Sure, he’d woken up needing to scratch an itch before, but this was different. It was overpowering, unbearable and everywhere at once. Tails yawned heartily and drug his claws along his coat to relieve at least some of the terrible itching while he kicked his bedding away from him. The sunlight shone lightly through his blinds, indicating it was a fair while past sunrise. Sonic would be awake, probably cooking based off of the smokey scent of frying bacon wafting up from downstairs that made his mouth water.

As a fox mobian, Tails’s dietary needs leaned more towards a meat and animal product based diet, as did most other carnivoran mobians. While Sonic as a rodent mobian could still technically consume meat, his preference leaned more in favor of plant products. Tails, too, could consume plant products in moderation, but the bulk of his diet was still favorably meat.

When he was much younger and had just met Sonic, Tails exhibited signs of serious malnutrition. Sonic had apparently made note of Tails’s sickliness, as one of the first nights traveling with Sonic, the hedgehog had pulled out an entire slab of bacon slices he’d bought and cooked them over the fire. While Sonic had barely any of it, the young and scrappy fox kit had scarfed down most of the meat like he was starving. Which, for all intents and purposes, he had been. Since that night Tails hadn’t ever truly gone hungry, always provided with protein-rich foods and three square meals a day as much as was feasible. When they’d settled down in a home in the Emerald Hill region, Sonic had insisted on filling it with the largest fridge his remaining money could buy so they could both store enough food for their respective diets.

Most mornings Tails would cook for himself, plenty old enough to know how to work kitchen appliances (even if he somehow didn’t have an IQ of three-hundred, of which trivialized most tech, let alone an oven). However, sometimes Sonic would insist on cooking duties; usually when Tails was sick, busy or it was a special occasion. Today of all days it was the latter. Tails’s thirteenth birthday had finally dawned, and it was a special one. After all, it wasn’t every day one finally, finally became a proper teen. It was no wonder Sonic had likely gotten up early as the sun to prepare and ensure Tails had a good breakfast before the party preparations.

Though Sonic wouldn’t call himself a sap by any means in a billion years, Tails absolutely knew he was. It wasn’t just anyone who’d adopt an orphaned fox kit at eleven years of age and raise him to impressive effect for the nine years following. Yet, Tails felt guilt. A hedgehog blessed with the mysterious power to run faster than the speed of sound, to explore the world and save it with his gift, and he tied himself down with a child. A child who needed a caregiver, yes, but a child was a big responsibility. To this day, Tails couldn’t fathom why he’d given up his nomadic lifestyle to ensure a (relatively) safe upbringing for a child he barely knew at the time. Tails doubted he would ever understand, but the significance wasn’t lost on him, and neither were the acts of love Sonic performed to remind him he wasn’t going anywhere. Bacon and who knew what else on the morning of his big thirteenth was just one of the many ways Sonic was absolutely, one-hundred percent, without a doubt the biggest sap on Mobius.

Tails yawned again and slipped out of his woefully comfortable and warm bed in favor of getting ready for the day. Slipping on his socks and gloves, he reached for a brush to brush out his fur. Though summer was just ending, Tails’s fur would be thin for a few weeks longer before the autumn chill set in and he shed his warm season coat for a thicker one. So it was fairly unexpected that when he combed the brush through one of his namesakes he saw a large chunk of fur break away from his pelt. Brows furrowed, he examined the puff of summer fur and found himself further confused by the fact the fur beneath was darker and thicker than the rest of his coat.

Tails’s fur had always stayed rather consistent in its coloration through the years, a light yellow-orange shade with little variation or pattern. The fur beneath his summer coat this time was more of an orange shade with yellow highlights and darker roots, causing Tails to pause in shock. He hadn’t been shedding yesterday, and shedding was always a gradual process. Tails was a practical fox, and knew there was no way these things happened that fast. However nice it would be in theory, he wouldn’t have just shed his entire summer coat overnight… Except, he had. Tails brushed elsewhere, along his forearm, and noticed the same occurrence. His coat color had changed somehow, and so suddenly. Not to mention it was much thicker and longer. A million thoughts passed through his head in that moment. Was he sick? He didn’t feel sick. Was this puberty? No, surely not just yet. Did he spill a formula in his workshop he didn’t read the label on? No, he definitely wouldn’t have done that.

A knock at his door jostled him from his thoughts.

“Hey buddy, you awake?” Sonic’s muffled voice rang through the door. Tails flinched at the volume. Sonic hadn’t been shouting, yet he pinned his ears in reflex as if he had been. Despite being caught off-guard, Tails forced a light tone to respond.

“Uh, yeah! Just getting ready!” he responded. Sonic chuckled on the other side,

“10-4, pal! Got breakfast ready when you come down,” and with that, Tails heard soft footsteps depart, further concerning him. Tails always had very sharp senses, but Sonic’s normal speaking voice had overwhelmed him, and he could hear the fibers of the carpet shifting beneath Sonic’s feet outside of his very much closed bedroom door as he departed.

“This is so weird,” Tails muttered lowly. He shook his head and resigned to finish brushing his fur out, even if he looked increasingly odd with his new fluffy coat and hue. A glance in the mirror on his writing desk had him pausing again to stare. He looked so… well, different was obvious. Strange was more like it. His bangs had lengthened out with the rest of his coat, but his facial fur had darkened considerably. A stripe of brown fur trailed from his nose along a bridge between his eyes, and his eyelids had darkened to a similar tone. His facial features still resembled him, however. The same sky blue shade of his eyes shimmered back at him with the uncertainty he felt. There was simply no way he shed and developed these patterns over night. Except he had. Tails’s stalwart practicality was beginning to ebb in the wake of a pit of anxiety in his gut.

The itching had begun to resume with gusto, causing him no end of annoyance as he exited his room and flinched at the sensory input. The scent of bacon was absolutely overwhelmingly strong. Tails wrinkled his nose in reflex and felt a bit of nausea as a result of the smell. He loved bacon, it was a bit of an uncomfortable feeling when he was nauseated by the smell of it. Swallowing his bile, he quickly made his way down the hallway and the flight of stairs leading to breakfast. However strong the bacon, he wouldn’t let it ruin his birthday breakfast.

“Hey lil bro!” Sonic’s voice rang out again, but Tails resisted the strong urge to flinch at its volume. He smiled as he rounded a corner to enter the kitchen and saw his older brother. The blue hedgehog wore a pair of hot pink oven mitts with a black apron depicting a spatula with the words “this shit is going to be delicious” emblazoned above it in bold lettering. Tails recalled buying that for Sonic some years back for New Year’s after he’d insisted he needed a proper apron for grilling his chili dogs. Ever since, it was his cooking uniform, along with the mitts that Cream bought him for one of his birthdays.

“Morning, Sonic,” Tails chirped, resisting the gag he almost succumbed to upon seeing the enormous pile of fried bacon on a large plate next to the stove. Under any other circumstance his mouth would water and he’d take at least half of the pile for his breakfast plate not counting seconds, but the sight made him queasy. Other plates were also set up along the rest of the counter. Easy-over eggs, sausages, cheese biscuits and even some sliced fruit adorned the large plates. It was actually really sweet that Sonic had gone all-out that morning compared to most breakfasts, and Tails so very much wanted to appreciate the effort and the flavors if he wasn’t about to dry-heave all over the kitchen floor in that moment.

“Mornin’. Happy birthday, dude,” Sonic pulled a hand away from his current pan of cooking bacon to ruffle Tails’s bangs. Tails held his breath, hoping against hope that maybe Sonic wouldn’t have noticed how long and fluffy his fur had become. However, it wasn’t to be. His brother knew a lot about Tails, down to the individual hairs on his head, and he had noticed a difference. Sonic’s hand flinched away slightly, before touching Tails’s bangs again, this time in an analytic manner. He turned his head to look, and his emerald eyes widened in shock, “woah.”

“Yeah…” Tails grimaced, shrugging his shoulders self-consciously. Sonic turned away from the cooking bacon to get a closer look at Tails, a pitching whistle accompanying his examination.

“Now, I know summer’s comin’ to an end, but I’m pretty sure you weren’t due for your winter coat yet, right?” Sonic queried. Tails nodded.

“Not sure what happened, but I woke up and my entire summer coat just kinda… fell out,” Tails explained, face still twisted in a grimace, “not sure why it looks so different.”

“Well, it’s new for sure, but it suits you,” Sonic tried to alleviate some of the anxiety that had leaked into Tails’s tone.

“Thanks…” Tails gulped against his queasiness, excited to get breakfast over with before he gagged on the permeating smell of glorious-yet-deplorable bacon.

As soon as the last of the bacon had finished cooking and been dumped onto the large plate, the pair had selected their food and sat across their small dining table from one another. Sonic had begun digging into his fruit and biscuits with gusto, while Tails simply picked at an egg with his fork in uncertainty. Though the active scent of cooking had dulled a bit, the remaining smell still caused Tails to feel unappetized, not to mention the sound of Sonic’s fork scraping against his plate.

Seeming to notice Tails’s lack of chowing down, Sonic looked up from his own food.

“You okay?” he asked simply. Tails resisted the urge to grimace and nodded lazily, still staring at his plate with trepidation.

“Just uh, not hungry, I guess,” he spoke flatly, trying not to betray his sickness, “’m fine.”

“Are you sure?” Sonic pressed lightly. Tails knew Sonic wasn’t an idiot, and that he wouldn’t be able to hide the fact he didn’t feel a hundred percent for long if at all. The hedgehog was probably already on alert from the sudden coat change. It wasn’t like Tails didn’t understand, he was pretty anxious too; it just wasn’t normal to shed this quickly and drastically no matter how you spun it. Yet, he felt hesitant to tell Sonic that everything was too loud, too smelly, too warm and too bright. He didn’t want to offend Sonic’s efforts, or give him any reason to cancel his party. Tails had waited thirteen years for this, and he didn’t want to disappoint his friends. Even if he would’ve rather been already rushing to his workshop to run tests on himself in paranoia to see if anything had somehow poisoned him, rather than partying.

“Yeah. Sorry, guess I’m just jittery about today,” Tails lied, “you only turn thirteen once and all that, right?” he plastered a fake smile, hoping it would be enough. Sonic didn’t immedietally respond, his eyes scanning Tails’s face for a few tense moments before he smiled.

“Hey, don’t sweat it! Figured we’d have leftovers anyways… Just try and eat a little, yeah? Don’t want you to pass out while we’re preppin’ for your big party.”

Tails didn’t eat even a little bit. Sonic had definitely noticed, even if his expression didn’t change from his signature smile when he grabbed up Tails’s still-full plate from the table. As Sonic worked away at cleaning up the kitchen and putting away leftovers, Tails chewed at the inside of his cheek as he thought deeply. Yet no matter what he puzzled together, he couldn’t piece together his odd symptoms. No sickness or disease he was even remotely knowledgable about matched his symptoms thus far, and it drove him crazy. He would need to check his poison and contaminant database twice just to ensure he hadn’t ingested something somehow on accident… So much work to do, yet none of the time to do it. His party would absolutely get in the way of solving this mystery, and it drove him a little insane to have to pick between potential mortal peril and his birthday party. Welp.

“How about we start with decorations since Vanilla said she’d handle baking the cupcakes this year?” Sonic offered. Tails blinked upon seeing Sonic had used his speed to finish the dishes in record time. Cheater… Tails quirked a smile despite his turbulent thoughts.

“Sounds good to me.”

~~~

Tails’s anxiety had only increased tenfold as the morning and afternoon melted away. The unbearable itching had continued, as well as a growing ache in his lower back and head making itself gradually more known as hours passed. His senses had dulled with the time to become used to them, but any time a sudden loud noise was made, Tails would flinch as if struck. Decorations had gone up, snacks had been put out, and his comical pile of gifts had been piled near what was likely to be the epicenter of the celebration in the living room. Tails was already flattered Sonic could think of so many gifts for him, not to mention the ones that their friends would bring as they arrived.

Flattery, however, did not make him feel any less like complete and utter crap. He had to take frequent breaks from any remotely strenuous work lest his head explode and his sight prickle with dark spots. Tails didn’t often get migraines, but when he did, he’d typically allow himself to rest and recover fully before pushing himself in any way. This was different, though, because it was his first and only thirteenth birthday. Excitement buzzed beneath his aches and itching, with a lingering and powerful desire to not disappoint his friends.

Tails continued to ignore his pains, which reached a distracting level by time Cream, Vanilla and the Chaotix arrived. The cupcakes had been obtained, fitted with thirteen candles and displayed proudly as the center of the snack table, but at what cost to Tails’s sanity? He tried to stay as awake as he could as Vanilla pulled him into a hug.

“Oh, you’ve grown so much, Tails!” her warm tone poured over Tails like warm honey into tea, and he couldn’t help but blush beneath his fur as she held his shoulders and looked over him with pride and maternal affection in equal measure. It was no secret that Vanilla the Rabbit had practically adopted nearly all of Sonic’s friends, himself included. While she wasn’t their full legal guardian, she typically signed paperwork for Tails that Sonic couldn’t (or wouldn’t, much to Tails’s appreciation). Her approval was like polished emeralds to Tails, a soothing balm over his validation-seeking heart when he needed it most. If Tails could ever call someone ‘Mom’, Vanilla was her.

“Heh… Thanks…” he bashfully looked down at the floor.

“It won’t be long before you’re competing against Sonic for height, either!” the matronly rabbit giggled kindly, “goodness, and your fur! You’re growing into your own, little one. I’m so proud of you!”

“Mother, stop torturing Tails!” Cream interjected in indignation. If Tails had a friend even remotely close to Sonic’s status, it had to be Cream. Once sweet as a sugar cookie, the young rabbit had developed a bit of a sharp wit to her boundless compassion in the past few years that rivaled even Tails’s own. They once were as far apart and different as the sun to the moon, but they’d grown close enough through forced playdates that Tails found himself genuinely appreciating Cream’s input on his projects, or even just her company.

“Oh, very well, sweetheart,” Vanilla tsk’d and brushed Tails’s bangs to the side before she pulled away, “I’ll go put our presents on the pile!”

“Happy birthday, Tails!” Cream congratulated as soon as Vanilla left the vicinity. Tails chuckled awkwardly.

“Thanks! Guess I’ll be hearing that a lot tonight, huh?” he sheepishly scratched the back of his head. Cream smirked and poked his nose teasingly.

“Yes, and don’t mope about it! You deserve it!” the young rabbit insisted, “thirteen is a big number!”

“Well, mathematically speaking–” Tails began, but Cream had none of it. She blew a raspberry and crossed her arms.

“It’s your birthday, no nerd thoughts!”

“You just want an excuse for me to not be right,” Tails snarked, no real bite to his words. He enjoyed banter, and only a few of his friends could truly participate in a way that was fun for him. Cream rolled her eyes with a smile.

“Keep telling yourself that! Nobody’s right all the time, not even foxes with three-hundred IQ.”

A knock at the front door interrupted any further dueling for the young pair. Sonic rushed to answer the door before anyone else could, and swung it open to reveal a familiar pair. Amy Rose stood in all of her glory, at least five presents stacked up in her hold with no effort. Next to her was Knuckles, a single large present tucked into his side.

“Heyyy, Knux, Ames!” Sonic welcomed the pair with open arms, but it wasn’t long before they honed in on the man of the hour.

“Oh, Tails! Look at you!” Amy cooed, still balancing her pile of gifts impeccably, “I swear, you’re getting taller by the day!”

“Yes… You’re growing up fast,” Knuckles nodded sagely, though a small smile betrayed his real feelings, as always. Tails chuckled.

“Thanks, guys,” Tails gratefully smiled, though the pressure in his head made it increasingly difficult to behave naturally.

Guest by guest passed by, wishing Tails a happy birthday or commenting on his growth. He did his best to mask his discomfort, and his sensory overload as more and more mobians made their way into the house and mingled. Cream seemed to notice Tails’s increasing difficulty keeping up a genuine smile. As Rouge and Omega made their way into the mingling crowd, she stepped back up to him with a concerned expression.

“Are you alright, Tails?” she sweetly asked, brushing a hand along his arm in a caring gesture. Tails blearily looked at her, and grinned as best he could. He didn’t want his friends worrying, even if he found his significant malaise souring his mood more and more.

“Yup! Doing fine!”

Cream didn’t seem to believe him, and opened her mouth to inquire further when the crowd suddenly went silent and a few of the lights shut off, stalling any opportunity to continue the exchange. A moment later, a green flash lit up the entryway of the house, and in its place stood a particular black and red hedgehog. The crowd remained silent for a moment, before Shadow opened his eyes and… smiled? As if that wasn’t strange enough, the typically isolated hedgehog walked up to Tails and looked over him with an appraising eye. Tense moments passed before he nodded in approval.

“Quite the turnout, Miles,” Shadow complimented, which was even weirder than the fact Shadow actually cared at all. Tails was never especially close with Shadow, the latter preferring business exclusive exchanges when he needed his motorcycle repaired or intel regarding a contact. Tails had tried small talk with the hegdehog before, but Shadow insisted on a professional relationship.

“Thanks… I think?” Tails was completely caught off-guard by Shadow’s friendly demeanor. The hedgehog’s apparent kindness seemed to run out after that, though, because he simply huffed dismissively and turned away to go stand next to Rouge. Huh…

“I guess that’s everyone,” Sonic noted nearby, “I guess Shadow decided to accept the invite after all… Welp, let’s get this party started!”

The party ramped up from then on, Tails cycling through the crowd in a daze. He could barely comprehend what was happening after a certain point, just nodding and smiling against the muffled words and glaring party lights. Eventually the opening of presents had come upon them, and Tails had tried to focus in to make sure everyone’s gift was appreciated properly. He really did try, but he got the sense some of his friends were expecting a different reaction to their various gifts. Many were thoughtful additions to projects, many more yet were knick-knacks or things he’d mentioned he liked or wanted in the past year, but the best gift (even to his rattled minds) had to be the giant tome that Knuckles had procured for him. Despite its apparent age, it was in remarkable condition. The pages were slightly frayed with time, but there was no doubt it was pristine for its time.

“It’s a book from Angel Island’s catacombs,” Knuckles explained, “it’s in a language I cannot parse, I don’t know what it’s about… But maybe you can figure it out.”

“I look forward to the challenge. Thanks, Knuckles!” Tails felt a jolt of excitement at being able to translate a never-before seen book, from the ancient echidnas no less! However, his malaise quickly returned in force, and his ability to keep up the ruse of ‘everything is fine’ was failing fast. Some of his friends looked at him oddly, and he yearned to tell them everything was okay, but he could barely keep himself aware of what was going on around him.

It was time for blowing candles before long. Tails could barely think of a wish, or really anything at all, before he was ushered up to the cupcake tower, all of his friends singing for him after a hushed moment of anticipation. The pleasant tune, which he heard every year since his fourth year, blended itself violently into a cacophony of voices.

A dull agony ripped through Tails’s skull and black spots fractured his vision. He groaned, or maybe he cried out, he couldn’t tell, but the singing had stopped. Tails held a hand to his forehead, sharp static buzzing through his mind and dulling all of his senses. The pain and itching reached a crescendo with his vision blacking out. A faint vibration spread through his back with the aching twinge throughout, making him vaguely aware of the fact he’d probably fallen over. Even fainter still were the alarmed voices calling his name from beyond the black, but his awareness was fading fast. He felt something warm and protective surround him, and he relaxed into the darkening of his senses. The last thing he felt was a hand gently slapping his cheek, and all became nothing.

~~~

Sonic knew something was off the minute Tails had walked into the kitchen that morning. The kit had stepped quietly along the tiles for one; Sonic could barely make out that Tails had come downstairs at all when he greeted him. If it wasn’t for Sonic’s keen hearing, he’d have probably been startled by his brother’s arrival. Tails hadn’t walked like that since he was very young, as if he were still in the forests of West Side trying not to be heard by predators and bullies.

The boy’s fur was a whole other issue. Sonic wasn’t stupid, he knew something was up. At first he thought maybe Tails had dyed it, like Sonic had said he would be allowed to do along with piercing his ears if he wanted to once he turned thirteen. He wouldn’t have blamed him for capitalizing on technicalities the very same day as his birthday. The fluffiness was new, though. Sonic thought maybe he’d brushed it in such a way that his fur fluffed out more than usual, but a good look at his coat was all he needed to know that Tails’s fur had developed new volume and colorations quite naturally.

It was all so weird already, but Sonic could’ve brushed it off. What Sonic didn’t brush off, however, was the fact Tails didn’t eat at all that morning. Tails never skipped on bacon, ever. The lack of appetite in his little brother concerned him considerably, along with his physical changes overnight. Sonic didn’t pry; maybe he was just getting a headstart on teenage mood swings? Maybe shedding prematurely was a part of development for him? It was uncharacteristic, sure, but what could he do? He didn’t want to cancel Tails’s party, and Tails seemed dead-set on pretending he was perfectly fine.

Sonic almost spoke up, though, when Tails needed constant breaks from the party preparations. Still, he didn’t speak up at all, because Tails said he was fine. Sonic trusted Tails implicitly. Oh how he regretted not saying anything, but by time he was certain something was seriously wrong, the party was in full swing. He could only watch helplessly as Tails continued to push himself through whatever illness had taken hold, still insisting he was fine.

Then they sang happy birthday, and Sonic watched what followed in slow motion. Tails’s eyes became unfocused and glassy, then began to shut as his legs collapsed under him. Sonic had just barely caught him before he reached the ground, a hand on his back to support him. The crowd gasped, various exclamations and shouts replacing the joyous atmosphere with worry and tension. In a rush of panic he examined the fox, noting how pale he looked beneath his fur.

“Tails?!” he exclaimed, eyes wide. Tails didn’t respond at all, prompting Sonic to gently pat his cheek and repeat himself. Tails still didn’t respond. A deep sinking dread replaced the anxiety he’d felt all day, “Vanilla!” he cried out. Not more than a moment later the adult rabbit was kneeling next to Tails, practiced eyes scanning him for injuries or apparent symptoms.

“I’m here, Sonic. Let me take a look at him,” she gently pried Sonic’s hands from the fox with some resistance from the hedgehog. Who could blame him? His brother, his child, had just passed out in front of him. Vanilla knew a thing or two about parental worry, even if Sonic insisted constantly Tails wasn’t anything more than his brother. Vanilla knew a parent’s gaze. She knew why Sonic always came to her for advice on raising Tails, why he stayed at her place in those early nights poring over legal texts and childcare books to ensure nobody could take him away. Tails was his brother in name, but Sonic was a father in his own unique way.

Though Sonic wasn’t related to Tails, he had put a part of himself into Tails in the same way Vanilla had given birth to a piece of her heart when Cream came into the world. And if anything had happened to Cream, she’d lose a part of herself in a way nothing could replace or console. So it was with double the resolve that Vanilla fell into her medical routine to ensure Sonic did not lose a part of himself.

Tails’s vitals were standard, no obstructions in his throat or lungs, and no apparent trauma had befallen him. Before Vanilla could continue her examination, though, she noticed something exceedingly odd. Turning Tails over, she saw a strange dark biomatter spreading along the back of his neck fur and upper back. She dared not touch the unknown substance.

“Stand back, Sonic,” Vanilla spoke gravely as the biomatter continued to spread along Tails’s spine and chest. She didn’t know what it was, but she wasn’t about to endanger Sonic if it spread. Vanilla was out of her depth, she realized, and stood. Whatever this was, it wasn’t natural or in her wheelhouse to treat. Sonic hadn’t moved an inch, so she grabbed his shoulders and tugged him gently away.

“But he’s still…” Sonic breathed, resisting Vanilla’s pull, “he needs help,” he croaked helplessly. Vanilla fought against her breaking heart at seeing Sonic so lost to keep them a safe distance from the ailing fox.

“I don’t know what’s happening to him, but I-” she was interrupted by a bright flash of blue emanating from Tails’s position on the floor. The crowd cried out in shock as Tails’s form was absorbed in the bright light, and Sonic felt his heart stop for a moment.

As soon as it began to dissipate, the biomatter was gone. The light fully faded and in its place was the same fox as before.

Except for the appearance of a third tail resting next to the other two.