Hello guys! I would like to thank you all for your support. My lastest four Big Hero 6 one-shots got a lot of attention and some people were asking for more (I have no idea why you'd ask me to write more, but thanks.)

So I've had this idea a few time ago. I wanted to write about Tadashi and young Hiro but I didn't want to make it an AU and somehow I wanted to make it last for a short period. This is what happened in my head. I hope this idea is not silly or anything.

This is my first fic for Big Hero 6 that isn't a one shot. I don't know how many chapters this will have, but it won't be very long. Maybe five or six.

That being said, enjoy!

"Imagine eating a sandwich but everybody just thinks you're crazy!"

Hiro laughed at his brother's friends as Tadashi introduced him to everybody. He was amazed by the machines and all the experiences around him. There were even some things that were unknown to him. He was not going to say that out loud, but he had to admit to himself that "Nerd's school" wasn't so bad. And those students were quite funny; mainly Wasabi and Fred. Hiro wondered how people that were so different could be such good friends.

"Hiro."

The young boy turned around and saw Tadashi standing on the door, motioning for Hiro to follow him. Hiro shrugged and followed the elder brother outside the room, walking with him through a corridor. They didn't say a word as Tadashi stopped in front of a door - which Hiro supposed would lead to Tadashi's lab. The younger tilted his head when Tadashi tried to open the door but failed.

"What's wrong?"

"Hum, I think I locked it earlier and I left the key in my motorbike. Why don't you go back to our Nerd's lab while I go get it so I can show you what I've been working on?"

Tadashi tapped Hiro's head before turning around and walking toward the main door. The younger one shook his head and considered following Tadashi outside instead of going back to a room of people he didn't know very well, but in the end he decided to go back to the lab. The students were back to their activities, so focused that none of them seemed to notice that Hiro was back. Except for Fred, that lifted his eyes from the comic he was reading and put it aside when he saw the boy entering the room.

"Hiro! That was fast. What's Tadashi working on?"

"Hey, Fred. Actually I haven't seen it yet. He went outside to get the key of his lab."

"Oh, that's cool. I bet he's working on something very powerful and awesome!" He looked up, then his eyes widened and he smiled as he looked back to Hiro. "Hey, do you want to see something I've been working on?"

"You? I thought you weren't a student."

"Well..." Fred said as he wrapped his arm around Hiro's shoulders and guided him outside the nerd's lab, toward a small room. "I'm not. But there's this guy who agreed to work on something with me and he said it's ready."

"What is it?"

"Come with me!"

Hiro followed a jumpy Fred with a smile on his face. They didn't have to walk much, for Fred's lab was in the next door. It wasn't exactly a lab; it was just a room with a table and several things around it, such as another lizard costume, an old tennis racquet, a pair of shoes and several clothes on the floor. Everything was dusty and Hiro tried to ignore that odd smell. He watched as Fred took off his costume and walked to the table.

"This is what I have been working on!" He said as he grabbed some kind of gun that was lying on the table. It was blue and purple, and small enough to be held with one hand only. Hiro made his best not to roll his eyes. He had seen the gun when he entered the room, but he thought it was a toy. He should have known Fred couldn't be working on anything serious. He decided to play along and approached Fred.

"So... What does your machine do?" Hiro said, grabbing the gun. He was surprised that it was way heavier than it seemed, causing him to use his two hands to hold it. A toy couldn't be that heavy, could it?

"Ok, so, you know how some grown up people become boring when they get older? I mean, you're a super fun kid but when you grow up all you can think about is paying bills, responsibilities, jobs... I mean, ew. This little gun is supposed to make people get back their old happy lives."

"Hum, wait, this is supposed to make you happier? Like a kid?"

"Yes! You get it! I knew it was real science." Fred said, proudly folding his arms.

Hiro turned his head and analyzed the gun he held. The concept was pretty good, after all depression and stress were serious things on that decade, but he could tell it was not going to work; for such machine was yet to exist, but the smile on Fred's face made Hiro shrug and nod.

"Pretty cool." He said, giving the gun back to Fred.

"Wanna test it?"

"What?"

"I've wanted to test it on someone for a while now, but nobody wants to do it because 'it's not science'. Nerds. I need a volunteer! And you were the first one who used a nice word to describe it."

Hiro bit his lip. He knew it was not going to work, but playing with guns was no laughing matter. What if it shot something that could hurt him? Then again, it was not going to work anyway, maybe it shot water or something like that. And it had been made by a man whose dream was to be a fire-breathing lizard. He sighed and shrugged.

"So, what will happen to me?" He asked, putting his hands on his pockets.

"You'll be happy like a kid again. You know, like me."

"Sure." Hiro rolled his eyes with a smile.

"Do you want to test it?"

"Hit me with your best shot." Hiro said, shrugging once more.

Tadashi was about to enter the Nerd's lab when he heard an explosion. It wasn't big, and at first he thought it was just Honey Lemon exploding another mess of her tungsten carbine, but then he noticed it didn't seem to come from inside that door. It seemed to come from somewhere else. He shrugged and entered the room. He looked around and heard some mumbling; his friends were also looking around. Hiro was nowhere to be found.

"Hey, guys. What happened?"

"We don't know." GoGo said as she looked around, suspicious. "We were trying to figure out where that explosion came from. Did you hear it too?'

"Yeah. It must have been in some other room." He then sighed and looked around again. "Hum, did you guys see Hiro? I wanted to show him something..."

"I haven't seen him since you two left." Wasabi said.

"Hum." Tadashi looked down. "Hey, Honey Lemon, did you see him?"

"No, sorry. I was trying to figure out a way to melt this without using fire."

"GoGo?"

"Don't look at me, I was trying to fix my bike."

"Fred?"

Tadashi expected Fred to answer him, but the silence made him realize his friend wasn't there either.

"Fred?" He repeated. "Where's he?"

"He may have gone home."

In that moment, Fred entered the room, rubbing his hands nervously.

"Hey, guys!" He said, avoiding eye contact. "How are you?"

"Hey, Fred." Tadashi said. "Have you seen Hiro?"

"Yes, but..." He stopped in mid-sentence as he bit his lip.

GoGo finally looked at Fred and popped her gum.

"I know that look. He did something wrong. What is it?"

"Well, I didn't do anything wrong... On purpose. And nobody got hurt, isn't it all that matters?"

"Fred." Wasabi folded his arms after putting a small piece on its right place on its table. "What did you do this time?"

Fred and the rest of his friends were on the hallway as the school mascot tried to explain.

"You see, I was trying to test this invention of mine and..."

"An invention of yours?" GoGo said as she folded her arms. "So that explains the small explosion we heard a few minutes ago."

"Yes, that was me. But it didn't go... The way I planned."

"Fred, quit the piffle talk. What did you do?"

"Well... Here you go."

He opened the door and closed his eyes as all of his friends opened their mouths in surprise.

Tadashi blinked and tilted his head. He pinched his own arm and mouthed "Ow", meaning that it was happening for real, but he refused to believe it. No, it had to be a dream or some kind of joke. That couldn't be real life. Wasabi shook his head, GoGo chocked on her gumball and Honey Lemon thought that she should start wearing a surgical mask when working, because something chemical should be affecting her brain.

In the middle of the room, sitting on the floor next to the table, there was a small boy. He should be around four or five years old, his eyes looked up and he seemed to be scared and curious at the same time. He had a very familiar face, and all the friends soon realized that they were in fact looking at Hiro.

"Fred." Tadashi said with an unreadable expression, never taking his eyes off the infant. "What the hell did you do?"

"Well, you see… I was trying to test this machine I built with a friend of mine and Hiro volunteered..."

"You tested your invention on my brother?! Fred! Do you realize..."

Tadashi trailed off as he turned to his friend. He had to do his best to keep him from strangling Fred, his face going red in both anger and confusion. He took a deep breath and closed his eyes, clenching his fists. After counting to ten, he was finally brave enough to turn his head again and face the baby once more as he tried to calm down. Honey Lemon was the first to approach Hiro. The baby shrank in fear and pouted, trying to hide behind the table. The blond girl made her best to smile and crouched down, wrapping her arms around Hiro and standing up. She tried to accommodate him, but he was fighting to get rid of her grip.

"Ok, you turned Hiro into a baby." GoGo said in disbelief. "How?"

"You see, I was trying to test this new invention and he volunteered. It was supposed to make people get back that happiness from their childhood and take away the stress of... 'Adulthood'. But it turned out... This way."

"Your invention. Fred, you were the man who tried to convince Honey to create a potion that would turn you into a lizard. How were you ever able of building something that actually worked? In a twisted way, I mean, but come on! You turned Hiro into a baby!" Wasabi said, trying to comprehend what was going on. "I didn't even know that was possible! It's just... How?"

"Well, I didn't do it on my own. You know that guy that used to study with you guys around three months ago? Red hair, a scar on his cheek..."

Everyone except for Fred and Hiro gasped in shock.

"What? You asked Andy 'Knucklehead' for help? Are you crazy?! We all know that guy isn't normal! I don't even know how he hasn't been expelled yet! You can't just go and ask him to help you to build you something like that! I wouldn't recommend saying 'good morning' to him, leave alone asking him for help!" GoGo said, nearly chocking on her gum again. "How could you be so irresponsible?"

Fred shrugged and looked up.

"Actually, we haven't seen him in weeks. I've heard he ran away because the police was trying to find him." Wasabi sighed, folding his arms. "I don't even want to know what that guy did this time."

"Well, he sure knows science..." Fred rubbed his hands.

Suddenly, their conversation was interrupted by a small wail. Little Hiro, who was on Honey's arms, started to get fussy. He tried to escape the girl's embrace, but she made her best to hold him tighter and keep him from falling.

"Hey, what's wrong, buddy?"

The baby put his hands on her shoulder and started to push himself away. He didn't want to be held, left alone be held by a stranger. He snorted and shook his legs, an angry expression on his face. He looked around the room and pouted, never quitting his efforts to escape her arms. It was when he laid his eyes on a tall boy with black hair and a cap. For a moment, he stopped fighting and gave a smile.

"D-D-Da..." The little boy uttered.

"Hum?" Honey said, trying to hold him in a confortable way again.

"Da... Das..."

"I think he's trying to say something. What is it, buddy?" Fred asked, approaching Honey and looking at the fidgety kid.

"Dashi!" He spilled out at last, shaking his legs. "Dashi! Dashi!" He reached out for Tadashi, who was standing a few feet away from Honey. He had a happy expression on his face, his big brown eyes sparkling as his hands tried to grab his older brother.

"I think he wants you, big brother." Honey giggled, approaching the older Hamada.

"What?"

"Dashi!" He called again, annoyed when he realized Tadashi wasn't moving closer to grab him like he wanted. He clapped his hands happily when Honey started walking toward his older brother, reaching out again and trying to touch Tadashi, who sighed and positioned his arms.

"Be careful, he's a little shaky. He might try to get out of your arms." The girl said.

Honey slowly handed Tadashi the kid, who was getting fussier by the second until he found himself in his brother's arms. His grumpy expression was soon replaced by a smile; he wrapped his arms around Tadashi's neck and buried his face on his brother's chest, letting out a relieved sigh and a yawn. The oldest brother blinked in surprise. He could remember his brother was very fussy when he was a baby, so he didn't expect Hiro to calm down out of nowhere.

"Aw..." All of Tadashi's friends said, tilting their heads as they watched the baby peacefully sleeping in Tadashi's arms.

"Guys! Focus! We have to concentrate here! My brother is five years old; we have to find a way to bring him back to his normal age, and fast! It doesn't matter how cute he is when he's..." Tadashi trailed off when he looked down and saw the infant in his arms, as peaceful as an angel. "Aw..." He then snapped back to reality and shook his head. "We have to find a way to fix this thing and bring him back to normal!"

GoGo held the gun and looked at it with a disgusted expression; Honey put her hand on her chin as she analyzed it.

"It's not my major, but... I think I can find a way to reverse this. I'll need everyone's help, though. I just need to find out what kind of chemistry that guy used to build this formula."

"Well, sure. Just tell me what I have to do and..."

Tadashi was interrupted again when Hiro let out another wail, this time louder. He rubbed his head on his brother's chest before opening his eyes and looking up at Tadashi's eyes, a grumpy expression on his face. His eyes were half open, showing he was tired.

"Dashi..." He moaned as he sighed and tightened the hug.

Tadashi tilted his head.

"I think the poor guy here is sleepy. You should take him home."

"What? I can't take him home! How do you guys expect me to carry a baby on a motorbike?"

"I can give you a ride, buddy." Wasabi said, putting his hand on Tadashi's shoulder. "Wait, what is your aunt going to say about this?"

"Don't worry, aunt Cass left the city for a week. She went to visit our grandmother earlier today because she's sick. It means we have one week to fix this. If she sees Hiro like this, you guys can say 'R.I.P Tadashi'." He said as he sighed. "Maybe we can start working on it tomorrow?"

"Sure. Don't worry, Tadashi. We're going to find a way. I'm going to keep this somewhere safe before someone else is turned into a baby here." GoGo said, being careful not to touch the trigger. "Now we all should go home. It's late and this little guy here seems to need some sleep." She said as she rubbed Hiro's head, that lied against Tadashi's shoulder.

The older Hamada sighed and nodded. They left the room and turned off the lights. He waved goodbye as he followed Wasabi to his car. He made his best to enter on the back seat with Hiro on his arms, trying not to wake the little boy up. As his friend started to drive toward Tadashi's house, he looked down at his baby brother and bit his lip. He could feel that it was going to be one crazy week.

"Here we are." Wasabi said as he parked the car and opened the doors of the car. "Are you sure you're ok?"

"Yes." Tadashi sighed as he left the car. The baby wailed a little when he stood up, but rubbed his face on Tadashi's shirt and went back to sleep. "I mean, he's already sleepy anyway. How difficult can it be? Besides, we're going to turn him back to normal tomorrow, right? It's just for one night."

"We'll try, buddy. Well, call any of us if you need anything."

"Thanks." Tadashi said and nodded as he walked up to the doorway. He watched as Wasabi drove away before reaching the key on his right pocket, trying to hold Hiro with one arm only. After a few fumbling tries, he finally managed to put the key in the lock of the door and turn it, entering the cafe.

"Ok, Hiro, we're home." Tadashi said with a nervous smile on his face as the baby blinked and looked around in curiosity, still sleepy. He went up the stairs and entered their room, sighing.

Tadashi put Hiro on his bed, helping him to lay down and covering him with the blanket. After Hiro seemed to be asleep, Tadashi sat down on the chair and put his hand over the bridge of his nose, letting out another sigh before closing his tired eyes. He needed some sleep and he was about to go to his bed when he felt something on his leg.

Startled for a moment, he looked down and saw his little brother sitting on the floor as he tugged Tadashi's pants.

"Hey, buddy. I didn't hear you leaving your bed. What's wrong?"

"Dashi." Hiro tilted his head and reached out, something Tadashi took as meaning "Grab me". He obeyed his little brother and soon the baby was snuggled up in Tadashi's lap.

"I honestly don't know what I'm going to do, Hiro. I have no idea how to take proper care of you and there isn't anyone I can ask for help. I'll do my best, ok? I don't know how long you're going to be like this, you could be back to normal tomorrow... Or it can last a little longer. Either way, I'm here, buddy. We're in this together, right?"

"Dashi." Hiro smiled.

"It's Tadashi." The older giggled. "Can you say it? Ta-Dashi. Ta. Say it with me."

Hiro put his tongue to his palate and forced it down.

"T-T-Tsh..."

"Ta..." Tadashi giggled again.

"Tashi!" Hiro said, clapping his hands, proud of himself.

"Ok, young man. You don't need to know how to say my name. Not yet, anyway."

"Tashi-Dashi." He smiled. "Dashi."

"Guess we're sticking with Dashi." He giggled. "I like the sound of it."

The young Hiro smiled.

"Time to sleep now, buddy. We have to wake up early tomorrow."

He stood up and put Hiro on his bed again, making sure he was confortable before going to his own bed. Tadashi took off his cap and put it on the nightstand beside his bed. He lied down and grabbed his blanket, but when he was about to turn off the light he saw Hiro standing near the separation blind.

"Hiro." He looked up and sighed. "It's time to sleep."

"Hun-gy." The baby uttered.

"What?" Tadashi said, rubbing his eyes.

"Hun-gy!" Hiro said, stomping his foot.

"You mean you're hungry? Oh, come on!"

Hiro pouted at his brother's tone, what made Tadashi feel guilty. He stood up and took Hiro's hand, walking with him to the kitchen. Tadashi rubbed his hair and tried to wake himself up, his eyelids going down, but he needed to feed his brother. He felt like it was a bad idea to give him anything sugary so late at night, so he walked up to the fridge as Hiro sat down on a chair and shook his legs happily. He could barely reach the table being five years old.

"Do you want some milk?"

Hiro nodded.

Tadashi smiled and put a glass on the microwave. He watched his brother as the microwave heated the milk and had to admit Hiro was super cute as a five year old. He could barely remember Hiro being that small once Tadashi was only four years older than him and their aunt Cass was a little too protective of Hiro when he was a baby; therefore he didn't get to spend much time with him before Hiro was ten. He snapped back to reality when the microwave started to beep

"Here." He said, putting the glass in front of Hiro as he sat down himself. He watched the baby drink it quickly in fast gules before holding his brother's hand softly.

"Now, now, you don't want to have a tummy ache, do you?"

"Dashi!" He wailed when the older kept him from drinking.

"Drink slower, ok?"

"Ok..." The baby uttered again before going back to drinking it. He used both of his small hands to hold the cup, which was a little too big for him. Tadashi kept his hands close to Hiro's face, in case he dropped the cup or anything. When he was done, he let out a yawn and a small burp that made Tadashi go "aw". Hiro wiped his mouth with the sleeve of his shirt and reached out for Tadashi.

"Dashi..." He said, sleepy.

The older sibling stood up and picked Hiro up from his chair, going back to their room. Hiro let out a happy sigh as Tadashi laid him down on his bed for the second time that night, but for the first time Hiro actually closed his eyes and snuggled up on his bed. Tadashi rubbed his brother's hair as Hiro yawned one last time and reached out for the stuffed animal on the desk. It was had been there since they were kids, but Hiro hadn't held it in years. It was a robot that Tadashi had given Hiro as a gift for his sixth birthday.

"Night, Hiro." Tadashi said as he stood up.

"Night, Dashi." Hiro said, closing his eyes. Within seconds, he had finally allowed himself to fall asleep.

Tadashi looked at his brother sleeping as he turned off the light. He didn't stop looking at him until he found himself in his bed, ready to sleep. It took him a while to finally close his eyes, just to make sure Hiro wasn't going to stand up again. He let out a sigh and turned off the last light, leaving the room in total darkness. Before he could finally fall asleep, he spent a few minutes reflecting on what had happened that day, and deep inside he hoped that was all just a dream, but he knew it was all real.

This turned a little different than I expected. Poor Tadashi, first night with little Hiro and he's already tired. This will most likely tell how Tadashi manages to take of his baby brother without having any experience on the subject while he and his friends try to figure out a way to bring Hiro back to his normal age. Yeah, it sounds a little boring, but writing it was fun.

Let me know what you think. Thanks for reading!