When you're going through your old stories and realize how embarrassing they were (ohmygod) but you can't erase them because they're contributions to your OTP's stories.

Author's notes: So I was going through my stuff, thinking where I should begin the huge project of rewriting my old fics when I stumbled upon this fluff. This really had huge potential but the thing was, the way it was written was so childish so I have to rewrite everything while still retaining the cuteness.

I noticed how annoying my old writing style was, haha. Kojirou and Jirou's name spelling weren't consistent, so I'm making sure I don't repeat that mistake. And some events are a bit too weird and of course, the grammar and the weird mixture of Japanese words and English words AND the annoying and unnecessary symbols are being removed (~). I'll stick to using the English words mostly and use only the "-kun", "-san" things so as to make them more in character.

Wish me luck! I hope I finish this first chapter before class starts in two hours, but it might be slow going because I slept in a wrong position and my left wrist hurts.

Box Animal Fever
Chapter 1

Yamamoto was going through his usual stretches and warm-ups in the park. Above him, Kojirou, his Rain-type Swallow was stretching his wings and soaring the sky, while beside him, his ever faithful Rain-type Dog, Jirou, happily kept up with his jogging, wagging his tail and panting excitedly.

All in all, it was peaceful morning with his 'Rain-box animals' and with all the fighting lately done in the name of Vongola, Yamamoto had almost forgotten what actual peace was like.

Not that he regrets meeting Tsuna and everyone else, he just wished that there were less fights and danger, and they could all hang out more often without something going wrong.

Yamamoto was jilted out of his thoughts, however, when he realized that Jirou was no longer beside him and was barking at something, not faraway. Tilting his head slightly in curiosity, Yamamoto took a one eighty turn, running back to where his dog companion was.

It seemed like Jirou wasn't the only one who derailed from their usual track, Kojirou was flying above Jirou, chirping softly. The blue swallow landed on Yamamoto's shoulder once he was close enough to look, nibbling on Yamamoto's ear in affection.

"Hey guys," Yamamoto greeted a bit breathlessly, "What do you have here?"

Jirou's tail was wagging wildly and he seemed to be excitedly yapping at something in the bushes. Yamamoto knelt down and looked closer.

He blinked in surprise when a pair of familiar sunset-colored eyes met his.

There was a soft mewl from the bushes and the young athlete leaned closer, balancing on his palms to get a better look at Natsu, Tsuna's sky-type box animal.

"Natsu!" Yamamoto said, surprised. "What are you doing here?"

The lion cub whimpered, his tail flicking in distress.

At the sound of distress, Jirou started whining, looking at Yamamoto then back at Natsu, as though imploring the rain guardian to help. Kojirou flew to the ground and hopped closer to the cub, chirping in worry.

Yamamoto crawled closer, spreading his hands in a comforting gesture. Natsu mewled softly, shyly coming closer to lick at Yamamoto's hand before nuzzling. The rain guardian smiled softly and carefully gathered the lion cub into his arms.

When he stood up, Jirou jumped up as well, paws landing on his stomach, barking questioningly.

"It seems like he hurt his leg." Yamamoto said, as though he knew that Jirou was asking him what was wrong with their friend. The rain guardian had noticed the way Natsu seemed to favour his right leg and the way he kept licking at it, as though trying to sooth his injuries.

Kojirou flew up and landed on Yamamoto's head looking down with a chirp.

"He'll be fine, guys." Yamamoto assured the two as he bundled the cub in his jacket, warming him and making sure he wasn't jostled too much. "I guess we'll have to cut our morning routine short, we have to take Natsu to my house and help him. Oh! And I also have to call Tsuna, of course."

With that, the three of them headed off to the Yamamoto household.

He was running through the unfamiliar, dark woods. He was panting harshly, his arms and legs were covered in scratches from the low hanging branches, he stumbled and fell so many times, and he's been running for so long he doesn't know what he's running from. He'd hurt his leg somehow, through it all, and he was half running and half-dragging himself away.

He finally stumbles through a familiar-looking clearing, falling to the ground. He pants and pushes himself up, and his eyes widen in horror and heart-stopping fear.

Instead of one dark oak coffin filled with white lilies, there were about a dozen of clear glass, coffins, each holding the bodies of his friends.

And right in the middle, kneeling by himself and crying was-

RIINNNGG!

Tsuna sat up, eyes flying open and panting harshly as he looked around wildly getting tangled in his bed sheets and falling to the floor in a blanket heap. "Oof!"

The brunet scrambled out of his blanket burritos, with a quick look around, he noticed Reborn wasn't here. Probably off doing some weird mafia business again…

RIINNNGG!

The brunet jumped and turned, realizing that it was his phone that was ringing. He picked it up, nearly dropping it when he saw Yamamoto on the calling ID. Thinking that something could have possibly happened again, his face paled, and his heart squeezed anxiously as he picked up.

"H-Hello?"

"Tsuna!" Yamamoto greeted at the other end of the line, the lack of distress in his tone eased the brunet's panic a bit. "I'm sorry for waking you up, but it's about Natsu…"

"Eh? Natsu?" At his Sky box animal's name Tsuna automatically turned to look at the small makeshift bed for the lion cub, his eyes widened when he noticed that it was empty eyes automatically going to the window, which was slightly open.

As though hearing the sudden skyrocket of the brunet's heart, Yamamoto quickly assured him. "He's fine, he's with me." The rain guardian said, quickly easing Tsuna's panic once again. "But I think he may have hurt his leg a bit because he got stuck in some bush."

Tsuna's froze as he remembered his dream, his hurt leg and the branches whipping against his skin, making him feel like he was trapped-

"-so I brought him back to my house." Yamamoto finished, telling what happened. Tsuna missed most of what he said. The young Vongola shook his head, trying to clear his thoughts.

"O-Okay, I'll come by right now. I'm so sorry, I didn't even notice he was gone." The brunet swallowed thickly, "I-"

"Hey," Yamamoto said softly, "It's okay, it's not your fault. Natsu's fine."

Tsuna nodded before realizing his rain guardian couldn't see him, so he cleared his throat and said, "Y-Yeah." He let out a tired breath, "I'll get us some breakfast first, as a thank you and I'll be right there."

"Okay, we'll be here." Yamamoto said, "Thanks for the breakfast treat."

"Least I can do."

"Oh good morning Tsunayoshi-kun!" Tsuyoshi Yamamoto greeted the brunet when he came through the door holding a bag of freshly baked meat buns from Fon's shop.

"A-ah, good morning." Tsuna bowed clumsily, "Sorry for intruding." He scratched the back of his neck sheepishly when straightened up.

"Nah, we're up earlier than this, no trouble. Takeshi's upstairs waiting for you and if those meat buns aren't enough you can always come down here for some sushi." The ex-swordsman said with a grin.

"Thank you." Tsuna said, bowing again before running up the stairs and tripping on its many steps.

"Yo." Yamamoto greeted when the door opened. He smiled at Tsuna over his shoulder and the brunet greeted him nervously.

"Sorry about this." Tsuna sighed, joining Yamamoto who was sitting on the floor. He sighed tiredly, "I should've noticed he went out, with my hyper intuition or I should have locked the window better-"

"Hey." There was a warm hand on his shoulder and the brunet looked up to meet Yamamoto's amber eyes. "It's not your fault and there was no harm done. Natsu just got a little lost that's all."

At the name of his box animal, Tsuna moved his gaze towards Jirou's dog bed, where Natsu was currently sleeping in. His right leg was bandaged and he was purring in his sleep. Jirou was cuddled up next to the cub, snuffling and ears twitching while Kojirou was nesting by Natsu's paws, eyes closed.

"I used the rain flames' soothing quality to help him sleep. Kojirou and Jirou helped of course." Yamamoto said, "Maybe we should call senpai to heal him?"

Tsuna looked at the clock on the wall.

"It's too early, I don't want to trouble him too." Tsuna said, frowning at the time and they had school too.

As though reading his mind, Yamamoto said, "I'm used to getting up at four in the morning, I'm always up at this time. It's no trouble."

Tsuna flushed, "Thanks." He said before reaching behind him for the meat buns. "Let's have some breakfast, school's about to start soon but I'm not sure if I should leave Natsu-"

"Jirou and Kojirou can look after him." Yamamoto assured him, "But if you really want to stay, I'll stay with you. Or we can put them back in the box and bring them with us to school-"

"No need." The window to Yamamoto's room snapped open. Reborn jumped in, a smirk on his face. "I'll look after them."

"Reborn!" Tsuna startled, jumping in surprise, "Where've you been?"

"Places." Reborn tilted his fedora, "Back to the subject, you can't afford to skip anymore classes, no good Tsuna."

"But- ow!" Tsuna whined when something small hit him on the head. The middle of his forehead was red from the shot, his rain guardian immediately went to get him a cooling spray.

Reborn blew his Leon BB gun, smirking at the young boss. "No excuses. I'm more than enough to look after Natsu and I have Yamamoto's rain box animals to help me."

"He's right." Yamamoto agreed, he sat down beside the brunet and took a look at the red spot. He cupped his hand over Tsuna's eyes as he sprayed the other's forehead. He placed the spray down and wiped his hand on a unused hand towel near his bag. "We have a lot of things to catch up in school and we can trust the kid."

"Smart choice." Reborn smirked, "Now eat your breakfast and head back home, Tsuna. Change into your uniform, I'll check later if you skipped classes.

The brunet sighed tiredly, "Fine."

Yamamoto got up with a smile, "I'll get us plates. Do you want anything to drink? We have milk, orange juice, tea…"

"I'll get it myself, I'll come and help." Tsuna said, getting up. When the two of them headed downstairs, Reborn turned to the three sleeping box animals.

"Hm," The hitman took out a new bullet looking at it with a critical eye and looking at the three box animals.

He smirked.

It was the longest school day Tsuna ever experienced and that was saying something.

The lessons seemed to drag on and all the teachers seem out to get him. Thankfully, he'd manage to avoid getting detention.

Ping!

Tsuna took out his phone to see a new message.

From: Demon Tutor From Hell

5:31:42 pm

Took Natsu back to your room, to avoid troubling the Yamamotos even more.

Tsuna raised an eyebrow at Reborn's message. He wondered how the small hitman managed to carry Natsu back to his house, seeing as they were basically the same size, only with Reborn having a bigger head.

"Hey!" A certain rain guardian called out, catching up to him. He was in his baseball clothes because he had practice. "The kid texted that he took Natsu back to your house."

"Yeah," Tsuna smiled sheepishly, "Thanks again for taking care of him and-"

"Nope! No apologizing." Yamamoto grinned at him, "Did the kid have senpai look at Natsu's leg?"

"I forgot about that," Tsuna exclaimed and flushed guiltily, "But knowing Reborn, he probably thought about it already and did just that."

"Yep, he's smart for a kid." Yamamoto grinned and Tsuna mentally sweat dropped.

'He's not a kid though.' Tsuna sighed internally. "Yeah, I'll be going back first to check on Natsu. You have baseball practice?"

"Yeah." Yamamoto smiled sunnily, happy to be back to his forte. "Senpai's got club practice too and Gokudera has detention again I think."

Gokudera got detention because one of the teachers tried to give Tsuna detention. He stirred up some trouble, making the teacher forget about Tsuna.

I am eternally grateful, Gokudera. Tsuna said, silently thanking the bomber's sacrifice. "Okay, well, I'll see you on the weekends?"

Yamamoto gave him a happy look, "Count on it!" He ruffled Tsuna's hair before turning and jogging back to the baseball field.

Tsuna ignored the venomous looks given to him by the students there, used to being scorned for being so close with the popular students (Gokudera and Yamamoto). He walked back home with his head down, careful to go through his usual shortcuts to head home, to avoid all possible bullies.

When he finally got home with no incident, the brunet sighed, relieved and headed inside. There was a note left near the telephone… His mom and the kids were playing at the park. The brunet took off his shoes and headed upstairs to his room, he quietly opened the door and closed it, walking towards his box animal pet who was curled up in his makeshift pet bed.

The brunet ran a hand through Natsu's flaming mane, the flames he produced were warm and he could sense a mix of rain flames as well, probably from Kojirou, Jirou, and Yamamoto. Tsuna had asked Reborn once, what other people who couldn't see flames, saw when they looked at Natsu. Reborn said that Natsu looked more like a cat than a lion to them, since his mane is just regular fur and wasn't as eye -catching as his usual flaming mane, and his eyes stood out because no one can really, truly hide the fire in their eyes.

Tsuna leaned forward and kissed Natsu gently on the head before getting up to change out of his uniform and fall into bed.

He was scared of falling asleep because he had a feeling that the reason Natsu went out that morning possibly had something to do with is dream. He's been having it for the past few days and he's always running and running and then he gets to that clearing, the clearing where his coffin supposedly was, where adult Gokudera had cried over him.

Only, it was so much worse, instead of his coffin, the clearing had the coffin of everyone he held dear. And right in the middle of it… was him, still alive, kneeling and suffering from what happened.

The brunet shut his eyes, covering it with his arm.

Ever since they returned from the future and the adrenaline finally seeped out of him and he was given the chance to breathe, his mind kept conjuring different scenarios of what could break the peace next and who would be hurt this time.

What if next time, he couldn't protect everyone?

Natsu whimpered on his tiny bed and Tsuna shook his head, dismissing his thoughts. Natsu needed rest and he needed to empty his mind.

The brunet turned on his side and buried his face into his pillow.

This time he was determined not to dream.

Half an hour later, deep in slumber, he didn't notice a certain arcobaleno creep in the room. Reborn turned towards Natsu, eyebrows raised when he saw the whimpering sky-type box animal. He raised his gun and pointed it at Natsu…

…and shot.

Yamamoto had a serious expression on his face all throughout practice. His teammates tried not to get in his way as much as possible, wondering (and maybe a tiny bit scared) about his strange mood.

The rain guardian had noticed the dark bags under Tsuna's eyes when he came in to get Natsu. Not wanting the brunet to close up or clam shut if he voiced his worries, Yamamoto pretended everything was all right until they got to school.

Tsuna, thankfully, didn't seem to notice anything amiss even when Gokudera flinched back in shock at his tired and pallid face. Yamamoto frowned and shook his head when Gokudera had opened his mouth to ask, so the bomber dragged him out of class while Tsuna tried to catch up on some sleep by napping before the teacher got in.

"What's wrong with the Tenth?" Gokudera demanded when they were outside.

"I don't know, I want to ask him but-" Yamamoto sighed, "He's been really cagey for the past few days and I didn't want him closing up just because we're worried."

Gokudera pursed his lips, looking into the classroom and right at Tsuna. "He doesn't seem to be sleeping well."

"When I called him this morning, he still seemed to be asleep."

Gokudera snapped to look at him, "What happened this morning?"

"Jirou and Kojirou found Natsu hurt in the park. He probably got out and tripped while he was running." This wasn't a far off possibility since Tsuna was clumsy and their box animals were basically a reflection of them.

The bomber crossed his arms, "We need to keep an eye on him and I'll try to ask Reborn-san if the Tenth is sleeping well."

"Okay."

"I'll protect him from getting detention as much as possible, the Tenth needs to go home early and sleep." Gokudera nodded decisively.

'And he needs to tell us what's keeping him up if he hasn't been sleeping.' Yamamoto thought to himself.

Yamamoto sighed in relief once practice was over. His performance had decreased because he'd been worried about Tsuna the whole day. He packed up his things and declined an invitation to eating out from his teammates.

When he finally got home, he noticed a black blur coming out of the window of his house. Yamamoto tensed automatically before he realized it was Reborn hopping over electric posts like they were nothing.

'That was the kid.' Yamamoto thought, confused. He went into the house, noting that his father was out. He closed the shop early because one of his friends in the shopping district was celebrating his birthday and invited him out for drinks.

Yamamoto headed upstairs and took off his shoes. Nothing seemed to be out of place. He headed to the bathroom, wanting a long, soothing shower before going to his room and reading a baseball manga when he heard a loud thump coming from his room.

Yamamoto tensed, eyes narrowed, before he grabbed his katana from his bag, he never left home without it now.

His shoulders tensed in worry when he remembered that Jirou and Kojirou were still out of their boxes and were in his room. Neither seemed to be making a sound, not even a bark or a chirp.

Yamamoto reached out and pushed his sliding door to the side, sword at the ready. A blur blocked Yamamoto's sight and before he knew it he was being tackled to the floor, sword clattering to the ground. Yamamoto tried to push back but the figure slumped over him, grip tight.

"Takeshi!" A familiar voice greeted him and Yamamoto blinked up, looking into familiar sky blue eyes and a familiar face.

"What-" Yamamoto huffed, pushing, "Who are you?"

The person pulled away and grinned down at him. Yamamoto blinked.

The very naked person… looked a lot like him, but only with blue eyes and dark brown hair.

"It's me, Jirou!" The guy named after his dog, of all things, said. "Welcome home!"

"Jirou," Came a calm voice behind him and the two turned to see another similarly naked, similar build, only with lighter skin and dark blue hair. He looked at them with a quiet smile. "Don't startle our master." He turned dark blue eyes at Yamamoto, "I am Kojirou and he is Jirou."

Yamamoto blinked and asked, "You're named after my box animals?"

Jirou laughed happily while Kojirou smiled in amusement, "No, we are your box animals."

Yamamoto looked up at them, eyes wide. "What?"

Tsuna felt too warm under his blankets his mind was somewhere in between sleeping and awake, never truly succumbing to slumber.

He shifted in the bed turning to the right, eyes fluttering as he tried to make sense of what woke him up. He blinked for a few minutes, before his eyes widen and he realized what he was looking at.

A pair of sunset-colored eyes was looking right at him at the corner of his bed and Tsuna jumped up and crawled backwards to the wall in surprised. "What- what- who?"

"Master?" Came a shy voice and Tsuna blinked when the light in his room suddenly came on.

"Ah, I see this is another failed experiment of Giannnini's." Reborn said after he turned on the light, a thoughtful look.

"What? What about Giannini?" Tsuna asked horrified, staring at the shy, naked kid about his age looking at him from the side of his head. "Who the hell is this Reborn and why- why is he-?"

"Naked?" Came a voice from the door and Tsuna looked up to see Yamamoto giving him an uncertain smile. "Hey, I think we have the same situation."

"Natsu!" Came a happy voice and suddenly tackled the naked, orange-eyed teen to the ground. He looked a lot like Yamamoto only with different clothes, hair color and eye color.

The teen 'eeped' as he was tackled and he fell to the floor.

"Wait, what!? EH?" Tsuna said looking at the two on the floor, "What do you mean Natsu?"

Tsuna's eyes bugged out when another Yamamoto look-alike came through the door.

The second Yamamoto look-alike smiled at him, "Hello Tsunayoshi-san, it's me Kojirou."

"WHAT?" Tsuna turned to Reborn in disbelief.

"I asked Giannini to develop a bullet that would allow the box animals to think in a more human level, which would have an advantage of raising out attack power since they would have the added human insight to defeat enemies along with their animal instincts." Reborn explained, though the explanation just flew through the brunet's head. "I thought, after receiving his memories from the future, that he'd somehow improve with his inventions however…"

Jirou was nuzzling Natsu's cheek while the younger-looking teen seemed torn between purring and whimpering. Kojirou sat beside them and had the manners to pull off the blanket on Tsuna's bed and cover Natsu with it.

It strangely reminded Tsuna of the time Yamamoto lent him his baseball jersey when he went into Dying Will mode.

"They turned to humans instead, which is equally as interesting as giving them the human capacity to think." Reborn said, smirking when Tsuna shot him a look.

"I can't believe you used Natsu as a guinea pig!" Tsuna said, upset. "And why are Kojirou and Jirou human too?"

Reborn tilted his hat, "I thought it would be fun."

"Reborn!"

"Ah, well it can't be helped." Yamamoto said and Tsuna shot him an incredulous look. The rain guardian smiled, "Either way, humans or dog or bird- Kojirou and Jirou are still themselves, they're still my friends."

At Tsuna's put out look, Reborn said, "Instead of complaining, no good Tsuna, why don't you actually do something and get your pet some clothes?"

The brunet jumped guiltily, realizing that Natsu is indeed still naked and shivering slightly. He rushed to his closet to grab a pair of sweatpants and a threadbare shirt. He nearly dropped said items however when he saw that Natsu was resting his back against Jirou's chest, while the ex-puppy rubbed his arms, trying to keep him warm.

Natsu's eyes lit up when he saw the clothes and he got up clumsily, tripping on the bed sheet. Thankfully, Kojirou kept him steady, "Thank you for the clothes, master." Natsu said to Tsuna.

The brunet swallowed, "M-Master" He shook his head rapidly, "Please, please do not call me that. You can just call me Tsuna."

Natsu just gave him a curious look and dropped the bed sheet to change.

"Hieee!" Tsuna covered his eyes and Yamamoto turned his face away, flushing lightly at the lack of modesty. But then again, these were animals.

"You're usually not easily cold, Natsu." Jirou commented from where he was still seated on the floor. "Being a human is so weird, everything is so much colder without your fur."

"Or feathers." Kojirou said.

"My mane was always so warm." Natsu mumbled as he struggled to wear the shirt. Kojirou helped him place his arms through the shirt and his head through the collar. He also pulled the long sweatpants over the clumsily worn boxers.

"Oh yeah, Natsu's mane was mostly made of flames. Figures he's always warm." Yamamoto said, when Natsu finished changing. "So, what do we do with them? I mean, I can ask my dad if Jirou and Kojirou could stay, but uh- do they eat human food? Feeding three teenage boys on a sushi chef's salary is different from feeding a dog and a bird."

"Don't worry about it." Reborn removed an envelope full of money from within his suit and threw it at Yamamoto, "Tell your father that they're friends just looking for a roof over their heads and that they'll take care of everything financial."

Yamamoto smiled gratefully, "You don't have to."

"Of course I had to, the Vongola family takes full responsibility. Take them out clothes shopping too, they can't always wear your clothes. In fact, since it's the weekend tomorrow, take useless Tsuna with you." Reborn said.

"Hey!" Tsuna huffed before he turned to Natsu who was sat again on the floor, with Kojirou leaning against his shoulder and Jirou sprawled on the floor yawning. "But what do we do about them when school starts? I mean, I don't think we should leave them, not when they're so new to being…" He gestured.

"You'll take them to school with you too, of course. They'll be enrolled by then." Reborn said nonchalantly.

"Wha-? But-!"

"No buts, you can't exactly leave them at home with nothing to do and you want to keep an eye on them. Obviously, the solution is to enroll them into your school." Reborn said.

"Yeah but- can they even read?" Tsuna grasped at straws.

"We can." Kojirou answered.

"Somehow, the Giannini's bullet made them human and retain a few human traits, the ability to act like a human, read and write." Reborn explained, "So, it's best for them to develop further in a learning environment."

Yamamoto nodded in understand and seeing his best friend agree easily, Tsuna sighed, running a tired hand down his face. Natsu was staring at Tsuna, his eyes worried. Sensing his worry, Jirou nuzzled Natsu's head in comfort. Yamamoto stared at the action while Tsuna was oblivious.

Tsuna finally said, "Fine. Do whatever you want. Let's talk about this tomorrow, right now…"

"I'll tell Maman about our new guest. Don't forget to set up a futon for Natsu." Reborn said turning towards the door, "Yamamoto you're free to stay for dinner."

"Nah, I think I have to head home and tell my dad about our new guests." Yamamoto said, shaking his head. "Do you know when they'll turn back?"

"I can't say, I have Giannini make an antidote though." Reborn said.

The athlete nodded, "Okay, I'll see you tomorrow, Tsuna."

"Yeah," Tsuna said, "We're still on for getting them clothes right?"

"I'll text you where and when." Yamamoto confirmed. Jirou got up from the floor and ruffled Natsu's hair. Kojirou patted the other intimately on the shoulder. "Sleep well!"

Tsuna waved at Yamamoto and his look-alikes. Reborn followed them out, leaving him and Natsu alone in his room.

What has he gotten himself into, now?

Author's notes: Come back of the animal box fever! Only with more substance and an actual plot!