Based on the absolutely adorable FOT AU from UponAGrayDawn on tumblr, incorporating some of the headcanons and that picture of Tadashi putting the scarf on Hiro. Just a little one shot. Hope you like it. :)

I swear I just went to sleep, Tadashi thought as his alarm went off. He felt the cold and didn't want to get out of bed. Tadashi had calculated that keeping it at 20C would save him $60 every month. Even the assistance housing cost a lot to heat.

He looked down and saw that Hiro had crawled into his bed in the middle of the night. Hiro held his blankie tight and was curled up. Tadashi sighed and sat up. He tapped on the space heater button with his foot, letting it come to life. Once he accidentally fell asleep with it on and Hiro woke him up. There was a piece of paper near it and it had caught on fire. It was funny now but Tadashi immediately went out and bought one that automatically shut off. The lady at the register knew him. She gave him a senior discount that he didn't ask for.

Tadashi ran through the checklist. Get Hiro to Headstart. Go to class. Work on lab. Pick Hiro up and eat lunch. Bring Hiro back to lab. Take Hiro to therapy, go to class. Pick Hiro up, back to lab. So on.

Tadashi made breakfast as Hiro stumbled out, his wild hair even crazier from sleep.

"Nii-san, hi," he said simply, and ran over to Tadashi's leg. Tadashi patted him on the head as he finished the eggs and dished them into a bowl. Hiro began to eat.

"Hey, 'Dashi, do we get to test your robot today?"

Tadashi grimaced. Last test ended with yelling, sparks flying, and quick thinking from Honey Lemon the chemist (and HAZMAT/fire extinguisher expert). Hiro thought it was all great fun, however.

"We'll try!" Tadashi finally said cheerfully. Hiro nodded and finished eating. Tadashi made himself some coffee and the two went to the bathroom to brush their teeth. Tadashi tried to comb Hiro's hair, but Hiro had "tender head" like their mom always said in her southern accent. Thinking about it still gave Tadashi a lump in his throat.

Tadashi put a hat on Hiro and wrapped a scarf around him. "It's cold out. Wear this, okay?"

"Mmkay," Hiro said, muffled. Tadashi threw his own cap and scarf on and they walked out.

They walked down the street to Hiro' daycare and he was dropped off. One of the girls flirted with Tadashi. It was flattering but the thought of dating was overwhelming. She thought it was cute he was taking care of his brother, like he had a choice. Like he would have even said no when the cops came to his dorm room, other students peeking their heads out. Tadashi didn't know how to react six months ago, and he still felt numb now. This was supposed to take time, the doctor at SFIT said. It was a lot to process. "Your chip can only handle so much," the doctor joked. He knew about Tadashi's experiments.

Tadashi took the uni shuttle downtown and listened to music. He dozed off against the window but someone else woke him up. It was Wasabi.

"Hey!" Wasabi smiled cheerfully. "How's it going?"

Tadashi sighed. "Tired."

"Yeah?"

"Hiro, man. He'll sleep for an hour, wake up, sleep again, wake up. Two or three times."

"It must be hard. I can't imagine. To be three and that happen?" Wasabi sighed. "Poor little guy. And I'm sorry you're not getting sleep."

"It's okay. It'll get better."

"That's the spirit," Wasabi said enthusiastically. They arrived at SFIT and Wasabi immediately sprayed his hands with antibacterial spray. "Those shuttles are nasty!" he said in defense when Tadashi gave him a look.

They went to their optical physics class, which was Wasabi's favorite. Tadashi took diligent notes. His professor told him about her own three year old, how she had rolled her little tricycle down a hill of San Fransokyo and scared everyone to death. Tadashi could relate. Hiro scared him constantly.

Tadashi ran over to Quantum Mechanics and had a great time working with Gogo on magnetic fields. He wrapped up his second class and ran to the lab. Honey Lemon was kind enough to make him a vinyl to try and stretch over his robot. He just had to sew the shape. Tadashi checked his phone. Hiro was having a good day-it was 11 and no one had called yet about a tantrum or a silent treatment or, worse, an electrical fire caused by Hiro trying to experiment.

Tadashi felt his neck ache as he sewed the vinyl in his industrial machine. Dr Callaghan, his advisor, walked over.

"Looks good!" he said encouragingly to Tadashi.

"Thanks," Tadashi sighed.

"How's home?" Callaghan asked.

"It's all right. We got approved for food stamps. Thanks for your help with finding the right forms."

"Hey, you and your brother are in a hard situation. And you are doing things to benefit others. You can accept some help too. Don't be afraid to."

"Yes sir," Tadashi nodded. "I have to go get Hiro."

Callaghan nodded and Tadashi took off, grabbing the uni shuttle back to his neighborhood. He walked to the daycare. Hiro was already waiting, bundled up.

"He wore the scarf all day, even inside!" Mrs Torrez laughed. Hiro looked at Mrs Torrez and grinned. Tadashi picked Hiro up.

"I've got sandwiches at the lab. And chocolate milk," he said. Hiro smiled and they said goodbye to Mrs Torrez.

"Thank you!" Hiro waved.

"You were so good today!" she said happily and sent them off. They took the shuttle back, Hiro looking with curiosity at the students with pink hair or tattoos. One of the women, with a blue Mohawk, saw Hiro and cooed. He lit up.

"Your hair is cool," he said.

"Aww thank you!" she smiled cheerfully. This was the Hiro Effect, Tadashi called it. Tadashi probably would not normally talk to people with blue hair and a tattoo that said NONCOMPLIANT on her neck but Hiro saw someone unusual and interesting and fun. He was friendly and in these moment, Tadashi saw the old Hiro, and a bit of his dad. Their dad could talk to anyone and find out everything about them.

"What's your name?" The girl asked Hiro.

"Hiro! And this is Tadashi, my big brother."

"Oh?" The girl looked confused. "I'm Anna. I'm a genetics major."

"I study robotics," Tadashi replied.

"Me too!" Hiro exclaimed.

"Oh yeah, you guys are in that lab they have to evacuate like once a week?" she asked.

"Yeah," Tadashi laughed. "That's us."

"Awesome. We only have to evacuate like once a month."

"What do you want to do?" Tadashi asked.

"My sister has phenylketonuria," she explained. "I'd love to find a way to turn nasty stuff like that off."

"PKU. I just loaded that into my database. I'm trying to create a nurse robot. It could do stuff like check your protein levels or warn you about your food."

"That's a great idea!" Anna exclaimed. "Stuff like that would be so helpful."

"Thanks. Genetics is a great direct way to help people. I wish biology wasn't so foreign to me," Tadashi laughed. "I read the stuff and input it in the database."

"Well, good for both of us," Anna said as they got off the bus. "Good luck, Tadashi. And Hiro. Hopefully your robot starts working."

"Thanks!" the brothers replied as she walked towards the Kekoa Hall. Tadashi and Hiro started towards the Seton Hall.

"Hiroooooo!" Honey Lemon cried with joy as he walked in. He ran to Honey Lemon and gave her a hug. "Check this out little guy!" she said and put a pair of goggles on him. "Okay. Classic experiment. I'm going to add some 30% hydrogen peroxide. Throw in some dish detergent. What color do you want?" she held out food coloring. Hiro picked green and purple and Honey Lemon added them to a large graduated cylinder. "Now I add potassium iodide and watch out!" she dumped the solution in and the two stepped back. Suddenly, the stuff in the beaker swelled like a foamy cloud and exploded up in a giant green and purple stream. There was steam coming off of the foam.

"Isn't that amazing!?" Honey Lemon asked and Hiro nodded in stunned awe. Tadashi laughed as Honey Lemon cleaned up and Hiro turned to Tadashi with the large goggles still on his head.

"Thanks Honey Lemon, Hiro will be trying to recreate that."

"There's a way to at home!" Honey Lemon told him.

"Yeah, no," Tadashi laughed as he took Hiro's goggles off and set them aside. He took Hiro's hand and walked to his own lab. He got out lunch and he and Hiro began eating. The new battery and vinyl had to be put on. Hiro busied himself with drawing as Tadashi put the vinyl on. He inflated it and the robot took shape.

"What should I call it?" Tadashi asked Hiro.

"It's a boy," Hiro told him.

"Oh. Okay," Tadashi laughed. "What should I call him?"

"Baymax," Hiro said without hesitating.

"Hey, not bad little bro!" Tadashi declared. "I like it."

Hiro finished eating his sandwich. "Thank you."

Tadashi desperately wanted to test the programming but didn't have time. "Let's go to Dr Jang."

"Okay!" Hiro jumped off his stool. Dr Jang's office was actually right near campus, two blocks from where Seton Hall was. They walked over and Dr Jang welcomed them in.

"Good afternoon!" he told them. "Everyone all right today?"

"Yes sir," Hiro nodded.

"Mr Hamada?" Dr Jang asked Tadashi.

"He's better. He went all morning without incident at daycare. Still has trouble sleeping."

"Good! All right, Hiro, you and me are gonna chat. And look! Here's my assistant Ms. Phen, here to help us!"

Dr Jang waved at Tadashi and Tadashi left, setting his alarm.

He ran over to his next class and was a bit late. History class, one of his last classes to mop up his core credits.

"Aw Mr Hamada, you didn't bring Hiro!" exclaimed Professor Jones. Tadashi made an apologetic face and sat down. He took notes. History wasn't his strong suit, but he enjoyed the chance to try something different. He thought of dropping it, and freeing up time to work in the afternoon and evening, but the social worker, James, talked him out of it.

"Your budget is airtight," he told Tadashi. "You keep it up and you can rely on your parents' life insurance and stay in school. You should. It'll make your life more enjoyable, and give you and Hiro a better chance in a few years, when you graduate." It was another bit of encouragement Tadashi needed. Those bits seemed to come just as he needed them most.

Tadashi finished up history class and ran back over to Dr Jang's office. Hiro was happily playing with blocks.

"He's doing much better. I see the sleeping issue going away soon. He's resilient. Little kids are. Are you still seeing Dr Choudhry?" Dr Jang asked.

"When I have money. Hiro's kind of the priority."

"That's okay. I understand. You're a good brother, Tadashi. Hiro's lucky to have you," he told him.

Tadashi thanked him and he and Hiro left to go back to the lab.

He typed in the computer, finishing his code. He put the chip in and said "Ow!"

Baymax booted up. Tadashi was nervous. This was his 86th try.

"Hello. I am Baymax, your personal healthcare provider."

"Oh my god!" Tadashi cried. "You're working!"

"Tadashi, what seems to be the problem?" Baymax asked.

"Nothing right now, but can you scan me?" Tadashi asked.

Baymax did so. "Male. 178 centimeters. 75 kilograms. Heart rate, 75 beats per minute and rising. Blood pressure, 110 over 80."

Other people were hearing this and gathered.

"Your dopamine levels are high. You are in a good mood."

"I am!" Tadashi exclaimed. "Hiro! It worked!"

Hiro was standing and staring at Baymax in wonder.

"Hello, I am Baymax. You have similar cranial features to Tadashi. Are you his brother?"

Hiro nodded. Tadashi heard Wasabi exclaim,"No way!"

"Is there anything else I can do to assist you?" Baymax asked Tadashi.

"No. I am satisfied with my care," Tadashi beamed proudly. Baymax waddled to his charge station and deflated. The others who had gathered began cheering, coming in to congratulate Tadashi. Hiro ran behind him and held him tight. Tadashi picked him up and gave him a big hug. Gogo slapped Tadashi on the shoulder.

"Good job," she told him simply, and walked off.

"That was like the biggest compliment I've ever gotten from her," Tadashi told Hiro. Hiro just smiled.

Hiro kept drawing and Tadashi wrapped up his notes and looked at the programming. A woman walked in, wearing a crisp business suit. "Sorry to intrude. My name's Abigail. My father is your advisor."

"Oh hey!" Tadashi shook her hand. "I'm Tadashi and this is my brother Hiro."

"I heard you got a machine working! That's great."

"Yeah, a nurse bot."

"Very cool!" she exclaimed. "My dad's really excited." She walked over and looked at Hiro's drawings. "What's this?" she asked.

"A robot," Hiro said. "Magnets."

Abigail's eyes went wide. "Like a toy?"

Hiro nodded.

"I work for a company and we just started a toy robotics division. Can I show them your idea?" she asked. Hiro nodded again. She took a picture of his drawing. "You may have a job as a toy designer!" she exclaimed.

She left and Hiro grinned at Tadashi.

"Hey!" Wasabi walked in. "Wanna go get some ramen?"

Tadashi looked at Hiro, who looked at him with begging eyes. "Oh yeah. We got a lot to celebrate."

They walked to the ramen house and ate happily, everyone sharing how excited they were for what they were finally accomplishing after so much hard work. Fred met up with them.

"That game was crazy," he sat down and pulled his beanie on. "What's going on with you?"

"Tadashi got his robot to work," Honey Lemon exclaimed.

"He-ey!" Fred clapped his hand on Tadashi's shoulder. "All right my man! And how's little man?"

Tadashi heard his phone ring. It was Dr Callahan.

"Yes sir?" he answered.

"Tadashi. The company Abigail works for-they love Hiro's design. They want to build it. I saw the picture. It's a genius idea."

"That's incredible," Tadashi laughed.

"They heard it was a little kid. They want to give him the creator's rights to the toy. That means if it's made and sells, Hiro gets paid a cut."

"Oh my god," Tadashi breathed.

"Tadashi, this is what you two have been working for. You should be proud of yourselves. I know I am," Callahan said, then said goodbye.

"Hiro, guess what," Tadashi said as he hung up. "Your little robot fighter guy? Abigail liked it. And so did her crew. They want to build it."

Hiro went wide-eyed. "Really?"

"Yeah," Tadashi nodded.

Hiro threw his arms around Tadashi in a hug and Tadashi smiled.

Tadashi took the bus home, holding Hiro. It was already dark and a bit rainy. He hurried from his bus stop. They had been robbed once on the street, in front of all the houses. Hiro cried about it for days.

They made it to the apartment door with incident and walked inside. Tadashi looked through the mail he grabbed. A few bills he would have to do some money magic to pay. Their SNAP card for groceries was in the mail. Tadashi shivered and put on a hoodie. He ran a bath for Hiro.

"'Dashi," Hiro said as he sat in the bath, playing. "Are we going to be okay?"

"Why do you ask that?"

"Sometimes...you're sad," Hiro's eyes fell. "You cry. And it makes me cry."

Tadashi felt guilty. He thought Hiro was asleep when he last let the fear and worry get to him.

"I'm sorry Hiro. It's been hard since mom and dad died. But we're gonna be okay."

"But if we are...why are you sad?"

"Just what people do, Hiro. You can know that it'll all be okay, but still get sad. You can miss people, worry about people, feel stressed about school. That's all."

"Okay. I get sad. I miss Mom and Dad."

Tadashi smiled sadly. "Me too."

He got Hiro out of the bath, and Hiro had him wrap him up like a burrito. There were declarations of eating the burrito, and the burrito laughed. Tadashi put Hiro in his pajamas.

"Can I sleep in your bed, Nii-san?" Hiro asked.

"There's not a lot of room," Tadashi told him.

"But when I'm with you, I don't have the scary dreams about being stuck in my seat."

Tadashi felt the gut punch. Hiro had been found in the car accident, hanging upside down, crying. Tadashi didn't like to think of it.

"Yeah," Tadashi barely said, his voice cracking. "You can."

Hiro grinned and grabbed his blanket, running into Tadashi's bed. Tadashi felt wiped. He had some work, but decided to do it on the shuttle tomorrow. He put his pajamas on and got into bed. Hiro snuggled next to him.

"Thank you for taking care of me. You're the best brother," Hiro said, and fell asleep. Tadashi smiled and felt, for the first time, that they really were going to be okay.