While I do not wish... to harm anyone... you should know... Baymax... that few are the men who... have challenged... me and lived.

Sunfire was a former member of the Big Hero 6. He also was a one-time member of the X-Men and former nationalist who changed his views after the death of his father. Possessing the ability to fly and generate super-heated blasts of plasma, Shiro became one of Japan's most prominent heroes.


Shiro was born in Agarashima, Japan. He was raised by his uncle Tomo as a child after his mother died from radiation poisoning caused by the atomic bomb dropped on Hiroshima during World War II. As a result, he was born a mutant possessing solar radiation abilities. Because of Tomo, Shiro was influenced to hate Western civilization and sought to restore Japan's former glory, despite the fact that his father was an ambassador to the United Nations. He attacked the United States Capitol until the X-Men intervened. However, Sunfire witnessed Tomo killing his father, prompting Sunfire to kill Tomo in a change of attitude. For his actions, he surrendered to the authorities and returned to Japan. Months after the incident, Sunfire was recruited to rescue the original X-Men from Krakoa, the Living Island. However, he denied that his assistance constitutes his becoming a member of the X-Men.

During his time as student, he also faced Dr. Kishi Oramosha, a brilliant businessman who turned into a villain calling himself Deadline and intended to wipe out Japan with a machine of his, named the Doomsday Device. Sunfire defeated Oramosha and had him arrested. Much later, Deadline would also face Big Hero 6, albeit without Sunfire.

When Magneto released an electromagnetic pulse across the globe, the energy overloaded Sunfire's body and caused his powers to flare out of control directly over Tokyo. This forced the Japanese government to imprison Sunfire, but he was soon freed by his cousin, the Silver Samurai, and Wolverine to help oppose a government plan to outfit giant Red Ronin robots with mutant-hunting technology. Battling one of the robots, Sunfire's powers again flared out of control and Wolverine suggested he seek aid from Canada's Department H, unaware that the Department had fallen into malevolent hands.

Informed by the Department's scientists that he had radiation poisoning, Sunfire remained with them seeking a cure. Unknown to Sunfire, the scientists had injected him with Zero Fluid, a compound that created an ambient charge of bio-kinetic energy within his body that conflicted with his bio-atomic powers and gave him problems controlling them. They falsely told him his powers and the fluid had formed cancer throughout his body and that he would have had to serve them for the necessary treatments. After refusing, Sunfire returned home instead, seeking refuge in an abandoned monastery.


Shiro can be very arrogant and temperamental at times, but greatly cares about his friends.


Sunfire dons a costume representing the rising sun symbol of Japan. With the Zero Fluid compound, half of his whole body turned jet-black.

Powers and Abilities

  • Martial Arts: Sunfire is well versed in the martial arts of karate and kendo, as well as the art of bushido: the history and customs of the samurai class.
  • Heat manipulation: Sunfire can biochemically ionize matter and convert it into the super-heated plasma state of matter, generating temperatures of about 1,000,000° Fahrenheit which he most often releases as force blasts from his hands. He can recharge and enhance his stored power by absorbing both solar and electromagnetic energy.
  • Infrared vision: Sunfire can view his surroundings in the infrared spectrum.
  • Flight: Sunfire can create super-heated air currents that enable him to fly while leaving a trail of flame behind him.
  • Psionic shield: Sunfire also generates an invisible field of psionic energy that protects him from the heat and radiation generated by his own powers, as well as from outside sources. The field also shields him from air friction and the light generated by his plasma, as well as lending a certain level of protection from kinetic impact.


When the Japanese organization known as the Giri began enlisting superhuman individuals to form a national superhero team known as the Big Hero 6, Sunfire was selected as a possible candidate, but later news about his supposed death spread. Young genius Hiro Takachiho mourned him, as the mutant was his idol.

Still, Hiro had hope and built a bio-atomic parcel detector specifically to be alerted if Sunfire ever returned. Though the technology was believed to be "impossible", it worked and one night, Hiro and his robot bodyguard Baymax went out to look for him.

Both found him at the monastery, but the excited Hiro soon became disillusioned to see his hero in the state he was. Sunfire tried to tell both to leave, accidentally throwing flames at them. Baymax's programming turned him into battle mode, fighting Sunfire despite trying to explain it was an accident and Hiro attempting to stop Baymax.

The fight was interrupted by Silver Samurai, Honey Lemon and Go-Go Tomago, with Sunfire falling unconscious. He was taken to the Giri headquarters and put under observation by scientists. Waking up, he saw Honey Lemon, who told him he should be treated as a guest and not a lab rat. Shiro noticed the scientists and polarized the window angrily, to tell Honey Lemon about his situation with Department H and that he no longer trusted any organization.

Hiro then went to the Giri building, where Mr. Oshima allowed him to visit Sunfire, who simply waited for his death by staying in bed. Hiro decided to leave and stop crying for him, remembering that he had gotten through his father's death already, and turned to the rest of Big Hero 6 for help, since an evil entity known as the Everwraith had recently kidnapped his mother.

The team went and fought Everwraith, unable to defeat him until Sunfire arrived to help, unaware that he was the villain's target. The Everwraith used his necroplasmic blasts to trap Shiro and attempt to cause an atomic explosion. Hiro told Sunfire to use his bio-kinetic fluid to counter it, but this only confused Sunfire. Hiro told him that he thought the Zero Fluid was part of his "treatment", so Sunfire finally realized he was lied to and wasn't dying. He then released all of his power on Everwraith, seemingly obliterating the ghost and himself in the process.

His teammates then held a funeral, but Hiro stayed for longer and saw Sunfire arrive, knowing that he had survived. Sunfire then tells him he has to find answers, and leaves the country headed to Canada.

Enraged, Shiro arrives some time after and breaks into Department H, looking for the doctor who had experimented on him, though he only found the Alpha Flight members telling him that the program had been terminated and there was nothing left of it. At that time, Big Hero 6 had moved to the Cool World Amusement Park with a new base, where they were attacked by a giant monster known as X the Unknowable. Hiro believed that only Sunfire could defeat it, so he revealed that he still lived and asked Honey Lemon to call him. Sunfire received the message. and hurried back to Japan accompanied by Alpha Flight.

The heroes helped clean the disaster and chased the monster until Sunfire sunk it into the ruptured Mount Fuji. After X's apparent demise, Alpha Flight return to Canada, while Sunfire decides to stay with Big Hero 6 in Japan once again. They also began to dismantle organized crime in Japan in order to clear the name of Clan Yashida.

Eventually though, Sunfire and the Silver Samurai would depart from Big Hero 6 for good, the former leaving in order to work at the X-Corporation office in Mumbai, India; and the latter gone because he had lost control of Clan Yashida, causing him to go back to his criminal ways and having his death faked after facing Elektra Natchios.

Sunfire's spot on the team was filled by Lumina, a young woman of the Coronarian species with similar solar-based powers. She went under the name "Sunpyre" in honor of Shiro's deceased sister, Leyu Yoshida, who had also used that name at some point. Silver Samurai was also replaced by Ebon Samurai, and with the two most experienced members of Big Hero 6 gone, Hiro became the team's new leader.


  • Sunfire, along with Silver Samurai, are the only founding Big Hero 6 members who are removed from the film incarnation, due to the company 20th Century Fox owning the film rights to the X-Men and related characters.
    • Ironically, the founding members of the film's team are Wasabi and Fred, who were the last characters to join the team in the comics.