Author's notes: This struck me like thunder and it's quite rushed. I'm sorry for any mistakes and discrepancies; I'll correct them once I get my breath back. Reviews are most appreciated and welcome!
When Tadashi is two, he likes helping his mother cook – even though his definition of 'help' usually constitutes of dragging a few plastic pots and pans onto the kitchen floor and stirring its contents with a wooden spoon. But Mother always smiles and strokes his hair when he does that, and that makes helping even better.
When Tadashi is four, he likes helping his mother take care of Hiro. Hiro's not big like him. Hiro's tiny and he can't walk. But Hiro has a mop of dark hair like him and Hiro has the same warm brown eyes. So even though taking care of Hiro means Tadashi can't go out to play, he doesn't mind. Because whenever he gives Hiro his favourite blue blanket or feeds him with his milk bottle or rocks him to sleep, Hiro always gives him a large goofy smile, and that makes helping even better.
When Tadashi is six, he likes helping Hiro when playing. Hiro can build amazing structures out of blocks and even more amazing robots out of anything they can scavenge at home (which included the dissected arm of a Spiderman figurine once). But Hiro only has two hands, and even though helping Hiro hold his 'equipment' means Tadashi can't play with his own toys, Tadashi's more than happy to do so. Because whenever he offers a new idea or glues the different parts they've found to make a new robot, Hiro gives a toothy grin and calls him big brother loudly, and that makes helping even better.
When Tadashi is eight, he likes helping Hiro measure his height. Tadashi would make his younger brother stand against the wall, mark Hiro's current height with a pencil, tell him to stop tip-toeing, then mark his actual height again. Even though doing so makes him think of mother, who used to do it for the both of them; of father, who'd laugh his booming laugh and tell them they'll be as tall as him someday; of Aunt Cass, who's warm and kind and amazing like mother but still not the same; Tadashi stops minding. Because when he sees Hiro's excited grin as he anxiously checks to see if he's grow any taller, Tadashi forgets all of that momentarily, and that makes makes helping slightly better.
When Tadashi is twelve, he likes helping Hiro bandage his cuts and bruises. Albeit the fact that after the fussing and bandaging, it is always followed by a half an hour lecture on how he should stop getting into fights with people and getting beaten up. Tadashi doesn't particularly enjoy seeing his brother hurt. In fact, he rather hates it. But even though seeing the white band-aids plastered across Hiro's arms and face makes his heart sting and ache, the grudging grin Hiro gives him and the thank you that always follows makes helping somewhat better.
When Tadashi is fourteen, he likes helping Aunt Cass place fresh flowers on the slabs of grey titled "Atsuko Hamada" and "Kiyoshi Hamada". She tasks him to do so when she's busy taking care of Hiro and the cafe. Seeing his parents again makes Tadashi cry, because he misses the way Mother would stroke his and Hiro's hair and he misses the sound of Father's loud and booming voice. Going in place of Aunt Cass reminds Tadashi of how much he still loves them and how proud they'd be if they saw Hiro now. Tadashi spends hours sitting down, talking about everything that has happened – anything he can remember – since his last visit, until the ache soothes into a dull throb and the tears have dried on his face. But Aunt Cass' relieved smile when he comes home, her eyes rimmed just a little bit red, makes helping a little better.
When Tadashi is sixteen, he likes helping Hiro with his science projects. Hiro doesn't actually require help with the content, per say. He just needs someone to reach the books on the taller shelves for him. It makes Tadashi thankful that unlike his younger brother, he's finally hit his growth spurt, because asking the grumpy librarian for a step ladder doesn't rank high on his bucket list. But even though helping Hiro pick up books at the library and giving him his own pencils and protractors to calculate the exact angle of San Fransokyo's largest bridge means Tadashi has to stay up later at night to finish his homework, Hiro laughs and stays out of trouble when Tadashi's around, and that makes helping a whole lot better.
When Tadashi is eighteen, he likes to help Professor Callaghan with the errands and tasks associated with being a university lecturer. Callaghan has salt and pepper hair, Callaghan speaks with a smooth and refined voice. But Callaghan reminds him of his father, regardless – still – and he's the closest thing Tadashi has to one after almost ten years. So even though helping Callaghan means being ostracised by most of the class because he's "sucking up" and being "a teacher's pet"; means having only four friends whom majority of the school population dub nerds (which Tadashi doesn't mind, actually, because they're all dedicated and amazing people); Callaghan smiles in a kind and fatherly way whenever he turns up in class, bright and early, and that makes helping a lot better.
When Tadashi is nineteen, he likes to help Hiro with his microbots. Because they're amazing, Hiro is amazing, and if Hiro can get into the San Fransokyo Institute of Technology, that'd be even more amazing. It means no longer having to worry that he's sneaking off to even more botfights and maybe being beaten up as Tadashi goes to the University for lectures. It means no longer having to worry about Hiro doing anything stupid that would jeopardise or even end his life. So even though helping Hiro means staying up half the night and barely staying awake in lectures the next day, Hiro looks at Tadashi with excitement and adoration that he only reserves for his brother, and that makes helping the best.
Tadashi's always liked to help. It's why he spends ages working on building Baymax, so Baymax can help others too (and maybe, if he's successful, victims of car accidents; like the one that took his parents). People have asked him about it before; about why he goes through such great lengths to help others – sometimes even at his own expense. And even as Tadashi tries to think of a comprehensive and detailed answer, his only reply is to shrug and say "Someone has to help." So why not him?
"Callaghan's in there. Someone has to help."
Tadashi does not make it to twenty.