Hiro's parents died when he was only 3 years old. He and his older brother Tadashi were then taken care of by their aunt Cass.
Hiro was 13 when he graduated from high school and he become a botfighter, causing trouble for himself and sometimes getting arrested, until Tadashi took him to see the college, the San Fransokyo Institute of Technology, where he was attending. At first, Hiro didn't want to go to college because he didn't like the idea of people telling him stuff he already knew. It was only after his brother brought him along to grab something from his lab on their way to another botfight that he changed his mind. When they were there, Tadashi showed him his lab and introduced him to his friends, showed him Baymax, a healthcare robot that he had been working on, and walked into professor Callaghan. Hiro was a huge admirer of his work and used some of his inventions in his bot for his fights. After that visit, the only thing Hiro wanted was to be able to attend the same college as his brother. To be invited to come and study there, he had to create something to impress professor Callaghan on the showcase day.
Upon arriving back home, Hiro set to work, but he was unable to procure an effective idea, believing he would never get into college. Tadashi then advised Hiro to "look for a different angle," causing Hiro to get an idea upon glimpsing his Megabot. Over the next few days, the Hamadas went to work on constructing microbots.
Eventually, the microbots were completed in time for the showcase. As the Hamadas and Tadashi's friends entered the showcase, Hiro was feeling nervous about presenting. At his turn to present, he stunned the audience with his microbots.
After the presentation, Hiro encountered Callaghan, who was with businessman Alistair Krei. Krei expressed a desire to have the microbots at his company, but Callaghan warned Hiro of Krei's nature before giving Hiro the acceptance letter.
In celebration, Cass offers to take Hiro, Tadashi and their friends back to the café for a free dinner, though Tadashi and Hiro separate to have some alone time. Once they're alone, Tadashi congratulates his younger brother on his success, proud to see him use his genius for bigger things in life. Suddenly, however, the school's fire alarm goes off, prompting Tadashi and Hiro to rush to the chaos. There, they see civilians escaping the showcase hall, which was mysteriously set ablaze. As Tadashi was helping people, one woman informs the boys that Callaghan is still inside the burning building and Tadashi decides to go in after him. Hiro tries to stop him, but Tadashi rushes inside anyway, not willing to risk losing Callaghan. Hiro then attempts to follow, but before he's able to, the building violently explodes, rendering him unconscious and killing both Tadashi and presumably Callaghan. A funeral and memorial are held and Hiro falls into deep depression at the loss of his brother and best friend. Cass tries to comfort her nephew, but to no real avail. As such, Hiro remains alone in his room, ignoring both Cass' attempts to cheer him up and his equally-saddened friends.
One day, Hiro accidentally stubs his toe and his pain accidentally summons Baymax, who was originally thought to be out of commission. Baymax explains that he heard the sound of distress and offers assistance. Hiro denies his offer, and tries to deactivate the bot, only to accidentally stumble upon one of his Microbots, which is still active and trying to reunite with the other bots. Hiro, thinking that the rest of his Microbots and the transmitter were destroyed in the fire, ignores the bot's activity, believing it to be malfunctioning and places it in a plastic container. Baymax, however, takes notice of this and acknowledges it, only to have Hiro sarcastically order Baymax to find out where the bot is trying to head, which the robot takes literally and does just that by going outside into the streets. Hiro chases after a wandering Baymax through the city and the two eventually find themselves at an abandoned warehouse. The two break in and they soon stumble upon a machine creating millions of Microbots. As Hiro ponders on the mysterious discovery, the Microbots rise and attack. Hiro and Baymax evade them hastily and eventually encounter a dark, masked figure named Yokai; the man responsible for the school fire and theft of the Microbots. The masked man pursues the duo, but they eventually escape at the last minute, immediately heading to the police station to report the attack.
The two give their claims to Officer Gerson, who dismisses their story as rubbish, thus denying them lawful assistance. Just then, Baymax begins to lose power, forcing Hiro to leave the station and return home to have the robot recharge. After sneaking past an oblivious Aunt Cass, Baymax begins to charge and Hiro takes a breather from the exhausting day. Just then, Baymax acknowledges Tadashi's disappearance, asking for his whereabouts. Hiro reveals Tadashi's unfortunate demise, and Baymax attempts to comfort him, but the mention of the fire being an accident sparks an epiphany. After the encounter with Yokai, Hiro realizes that the fire was no accident and recruits Baymax into helping him take down the masked culprit, wanting to avenge his brother's death. As such, Baymax is given a few new upgrades, including a super-suit equipped with karate-like battle programming and a new programming chip, which gives him such abilities. After his new upgrades are put to the test, the two head out back to the warehouse to find and capture Yokai. They arrive at the warehouse, only to find it vacant. However, using the last Microbot to track him, Hiro and Baymax are led to the docks, where they find the demonic Yokai emerging from the fog with a massive piece of technology. The two go into silent hiding until Honey, Go Go, Wasabi and Fred arrive, having followed the two there after spotting them snooping about the city alone.
Hiro urges them to leave, until the group is attacked by Yokai. Baymax tries to battle the masked villain, only to be thrown onto the top of Wasabi's van. The gang retreats from the scene with Yokai immediately following behind them, leading into a car chase throughout the city. Yokai makes several attempts to kill the team, but luckily, with Go Go's reckless driving, they manage to escape by driving off a ledge and into the bay, having Yokai believe them to be dead, thus promoting him to vanish once again. Baymax manages to rescue the team by removing his suit and floating them back to shore and Hiro suggests they needed a place to rest for the night, to recover, the group heads to Fred's mansion home. There, they ponder on the true identity of Yokai and how to find him before Baymax reveals that he scanned the masked man's body, allowing them to track him down via body temperatures and other health-related attributes. Before the mission to bring Yokai to justice begins, Hiro decides to upgrade both himself and the rest of the team, believing they'd have a much better chance if they all join together as superheroes.
After some scientific modifications and training, the group of friends become the team "Big Hero 6", bent on taking down Yokai. To do so, the team believes his mask is his source of power and the objective is to retrieve the mask to cease his control over the bots. Baymax is the last to be upgraded and after his new super-suit is revealed, therefore creating Baymax 2.0, he and Hiro take a test flight for the first time throughout the city, eventually landing on one of the air balloons towering over the city and overlooking a sunset. Hiro and Baymax take the time to relax and bond for a short moment, which brings happiness to the boy. Realizing this, Baymax asks Hiro if he's satisfied with his care, as his true objective throughout their adventure is to ensure Hiro's happiness and satisfaction, claiming Hiro to be his patient. Hiro denies Baymax's suggestion and returns to the matter at hand.
After scanning the city to find a match to Yokai's health information, Baymax discovers a match on an island not far from the mainland. The team heads to the area, which is revealed to be an abandoned facility placed under quarantine. There, they find a machine in the process of restoration, but are unable to uncover what it is exactly. Soon enough, their snooping leads to a room with recordings taking place in the facility. After watching, they learn that the facility originally belonged to Alistar Krei and the machine was a portal meant to enhance transportation. The test subject, a woman named Abigail, was the first to try it out, but as she did, the machine malfunctioned. Instead of calling off the procedure, Krei insisted that they move forward, resulting in a tragic accident that left Abigail lost in the portal and apparently killed by the machine's destruction. The incident resulted in the closure of Krei's facility. The team then comes to the conclusion that Krei is responsible for stealing the Microbots in hopes of rebuilding his portals.
Just then, Yokai appears and attacks once more. A battle follows and in the process, Hiro accidentally removes the villain's kabuki mask. Yokai's true identity is then revealed to be Professor Callaghan. Callaghan confesses his crime of stealing the Microbots and reveals that he used them to escape the fire alive and unharmed, meaning that Tadashi had died for nothing. A heartbroken Hiro tearfully explains that Tadashi died trying to save the professor, but Callaghan coldly responds by blaming Tadashi for his own death. Enraged, Hiro orders Baymax to kill Callaghan. Baymax denies such an action, explaining he's unable to bring harm to a human being, but Hiro, blinded by hatred and grief, removes the robot's healthcare chip, leaving only his programming of battle and destruction, thus sending him on a violent, mindless rampage in an attempt to kill the professor. Seeing this, Go Go, Fred and Wasabi try to fend off the bot and, in the mix of the chaos, Callaghan managed to retrieve his mask and escape.
Luckily, Honey recovers Baymax's healthcare chip and restores the robot to his original peaceful settings. Realizing what he's done, Baymax apologizes to the team for causing harm, but Hiro berates them, blaming them for Callaghan's escape. The team retorts by explaining that the plan was never to kill Callaghan, but instead, to merely apprehend him. Leaving the team on the island out of anger, Hiro and Baymax return home to repair Baymax's suit. Baymax talks to Hiro about the situation of killing Callaghan, asking if his death would appease the boy. Instead of answering, with his mind clouded by thoughts of fury, revenge, sadness and the loss of Tadashi, Hiro breaks down in tears. Baymax comforts him by showing him videos of Tadashi, which he recorded during his creation process. Tadashi's presence and loving words bring enlightenment to Hiro, who thanks Baymax for his comfort. Honey, Go Go, Fred and Wasabi soon arrive as well. Instead of being upset with Hiro, they, too, comfort the boy, he says he is sorry for yelling at them and they understand that his actions were only out of grief and vows to bring Callaghan to justice and his four teammates forgive him. Before they set out, the team shows Hiro a recording they found, which reveals that Abigail was the daughter of Callaghan and the entire goal behind his villainy is to extract revenge on Alistar Krei.
The next day, Alister Krei is in the middle of an important showcase, just as Yokai arrives and captures him. Yokai reveals himself to be Callaghan, and the villainous professor subsequently reveals his plot to use the newly-recreated portal to destroy both Krei's new building and Krei himself. Alistar tries to talk sense into the villain, explaining the incident with Abigail was an accident, but Callaghan ignores him and proceeds with his plot. Just then, Hiro and the team arrives on the scene. Instead of immediate attack, Hiro tries to sympathize with the professor, explaining the fact that extracting revenge isn't the way to handle his daughter's death, but Callaghan's fury gets the better of him, and his plans proceed. Hiro and the others battle the villain, aiming for Callaghan's mask, but Callaghan soon gets the upper hand with the help from the Microbots and leaves the team members to die as his plot is set in motion. As Hiro is being pulled towards the portal, his distressed team members call to him for help, while at the same time, he sees several Microbots being sucked into a portal, giving him a new idea. Hiro then uses the words of wisdom from Tadashi to successfully guide each of his friends to safety.
After being rescued by Baymax and rejoining the others, Hiro relays his new plan, instructing the team members to take out the Microbots and get them sucked into the portal to eliminate Callaghan's source of power, whilst he and Baymax take on the villain, themselves. Hiro and Baymax fly to attract Callaghan's attention, making him fire towers of Microbots in their direction. Dodging the Microbots, the two fly the point where they are almost sucked into the portal, from where Hiro orders Baymax to dive and break apart the Microbot formations to send them into the portal. Eventually, Callaghan captures the duo and prepares to make the killing strike, only to find that he has run out of the remaining available Microbots, thus rendering him powerless and vulnerable. With this revelation, Hiro and Baymax break free of their confinement and launch towards the villain. Fearfully, Callaghan prepares for his supposedly oncoming demise, but much to his shock, Hiro decides to spare his life, wanting to follow the moral code set by Baymax. Instead, Hiro and Baymax swipe the mask of Yokai and smash it into smithereens, causing Callaghan to finally (and permanently) lose control of the Microbots.
With his plans foiled and power-stripped, the team apprehends Callaghan, but Baymax senses life within the portal, though the being is said to be in hyper-sleep. Hiro realize that it must be Abigail and the young boy journeys inside to save her, along with Baymax. The two soon find Abigail, asleep in her capsule, and as they make their escape, some of the debris from the destruction of Krei Tech strikes them, causing Baymax to lose most of his armor. Hiro reaches out for Baymax, who manages to grab ahold of his hand, but they both find that the portal is soon closing. Baymax decides to use his rocket-fist to send both Hiro and Abigail to safety, and requests deactivation at Hiro's command. Realizing that this will result in the robot's permanent imprisonment within the portal, Hiro denies such a plan, not wanting to lose him. Baymax disregards his own safety to help of Hiro, reassuring his friend that he'll always be with him. Without a choice, Hiro tearfully hugs Baymax as he bids him farewell, telling the robot that he is satisfied with his care. With these words, Baymax sends Hiro and Abigail off, leaving himself trapped in the portal and eventually destroyed. After Hiro and Abigail manage to make it out of the portal, seconds before it explodes, Hiro reunites with the others and reveals Baymax's demise. Soon afterwards, the police and paramedics arrive to care for Abigail and arrest Callaghan.
Following these events, Hiro has made a tremendous recovery from his depression as he spends his days hanging out with Honey, Go Go, Wasabi and Fred. Finally joining San Fransokyo Tech as an official student, Hiro settles in Tadashi's old lab, where the young genius stores Tadashi's hat in his memory and Baymax's last piece of armor: his rocket fist, reminiscing of their time together fondly as he comes across it. Within the grasp of the fist, however, Hiro discovers Baymax's original programming chip (which contains both his personality and memories). After some work, Hiro is able to restore the robot, reviving him from his demise and reuniting at long last. The two rejoice in their reunion with a loving embrace and Hiro reassembles the Big Hero 6 team, dedicating themselves to protecting the city from any and all problems, thus finally putting his incredible potential to great use as Tadashi had always wanted.
During the credits, Hiro, along with Baymax, is seen hanging out around the city with his friends and watching television with Cass and Mochi. Newspapers show that Hiro has been awarded a grant from the university and the Big Hero 6 team performing heroic deeds around the city. Another newspaper shows a ceremony of a building dedication in Tadashi's name taking place, in which Hiro accepts the honor on behalf of his late brother.
- He graduated high school at the age of 13.
- In Fan Friction, he takes on the codename "Captain Cutie" after being named as such in Karmi's fanfiction, as well as the name becoming popular among the students of SFIT and even in the villain community, with Momokase using the name on the news. Out of all members of Big Hero 6, he shows the most disdain for his interpretation in Karmi's stories.
- 5 appearance(s) of Hiro Hamada (Earth-14123)
- 32 image(s) of Hiro Hamada (Earth-14123)
- 1 item(s) used/owned by Hiro Hamada (Earth-14123)