You took everything from me when you sent Abigail into that machine. Now I'm taking everything from you.

Robert Callaghan, also known as his alter-ego Yokai, is the main antagonist of Big Hero 6. He is a former professor at the San Fransokyo Institute of Technology and is the father of Abigail Callaghan.


Callaghan has a military background,[2] but later turned his goals to science and technology. Once a renowned scientist, he was an aspiring man with the ambitious hope of using his research to make the world a better place. He was recognized for his work in the fields of robotics and was the creator of Callaghan's Laws of Robotics, as well as the Callaghan-Catmull spline.

Later in his life, Callaghan became an instructor and the head professor at San Fransokyo Institute of Technology to mentor the new generation of prodigies. One of these students, Tadashi, admired him greatly. Though Callaghan was passionate about his work, his daughter Abigail was the light of his life. Callaghan was shown to support Abigail up to adulthood when she would become the test pilot for Krei Tech Industries under Alistair Krei. One day, Krei founded Project "Silent Sparrow", an experimental portal design meant to revolutionize teleportation technology. However, during the experimental test run, the portal experienced a malfunction and was forcibly shut down, trapping Abigail in the space between the portals. Callaghan, who was present during the test, snapped and tried to assault Krei in a fury, blaming him for losing Abigail.

The event catalyzed a transformation in Callaghan—he began to descend into madness, growing more unstable and obsessed with revenge towards Krei. Ultimately, this would lead to Callaghan discarding any semblance of his former self and the birth of the villainous entity known as Yokai.


Callaghan was a highly intelligent man who sought to teach young people and make the world a better place. He does not like when people try to do things the easy way or take shortcuts to get to their goals.

When his daughter Abigail was lost, he believed her to be dead and was consumed by rage and desire for revenge against Alistair Krei and his company, who were responsible for it. He kept his daughter's "death" to a minimum exposition and still appeared relatively calm after it, but behind the scenes, he planned a way to get to Mr. Krei and destroy everything he had as payback. As a direct result of his loss, Callaghan's mental and physical health was borderline turbulent, which even Baymax's scan of him diagnosed with acute stress disorder, high risk of cardiovascular disease, and emotional instability.[1]

Upon getting a hold of the Microbots, he faked his death and became relentless, doing his plans anonymously and in secret. Because of this, he did not care about hurting anyone getting in his way, even if it was people that cared about him.

Still, after Abigail was revealed to be alive and brought back, for a brief moment, Callaghan's face expressed silent repent, hinting he regretted his actions once he was incarcerated.


Callaghan is a middle-aged man who has blue eyes, grey hair, and slightly wrinkled skin. He was often seen wearing sweater vests and slacks.

Upon becoming Yokai, he wore a white, yellow-eyed Kabuki mask with red stripes to hide his face and dressed in a black trench coat, stealth suit, black gloves, leg wraps, and ankle-length ninja boots.

After being incarcerated, Callaghan wore an orange prison uniform, which indicates the status of medium-risk.

Powers and Abilities

  • Genius-level intellect: Callaghan was originally an inspiration to lots of young geniuses due to his many inventions and became the dean of the SFIT because of this. He had enough coordination to keep many Microbots doing different things at once.


  • Neurotransmitter: A high-tech headband designed by Hiro and used to control Microbots, attached to a Kabuki mask to hide his true identity.
  • Microbots: Callaghan stole Hiro's microbots and due to being the inventor of the Magnetic-bearing servos, he was able to make more for himself in secret to attack Krei Industries.


Tadashi introduced Hiro to Go Go, Wasabi, Honey Lemon, and Fred at the Ito Ishioka Robotics Lab; before leaving, Hiro met Callaghan, who compared the young man to his daughter as both loved Bot Fighting, then told Hiro he could join the SFIT, despite his age. Hiro was excited by this and created the Microbots to showcase at the SFIT student exposition, hoping to join the school. Both Callaghan and Alistair Krei attended it, being impressed with Hiro's project. Mr. Krei approached Hiro first offering to buy the bots, but Callaghan advised Hiro not to do it or he would not exploit his whole potential, also treating Mr. Krei with disdain. Hiro agreed not to do it and Mr. Krei left. After most people had already gone away from the exposition, Callaghan set the place on fire and shielded himself with the microbots to fake his death. Unknowingly, Tadashi ran inside looking for him, resulting in Tadashi's death from an explosion. Both were mourned by their friends and family at Lucky Cat Café.

However, Callaghan still lived, adopting the identity of Yokai to work secretly to attack Krei Tech Industries and obtain revenge. Hiro managed to save a single encased Microbot which started acting weird, leading him and Baymax to an abandoned warehouse where they saw more Microbots being produced. Yokai spotted them and began chasing them, but both managed to escape. After their encounter, Hiro went to the San Fransokyo Police Department to file a report, but the man attending them acted skeptical and uninterested due to how unrealistic the description sounded. Because of this, Hiro decided to take matters into his own hands, designing armor for Baymax and giving him a battle chip to fight against the mysterious man.

The duo went back to the warehouse, but Yokai had already left the location empty of any trace. Hiro's Microbot once more tried to reunite with the rest of the bots and so they followed again, being taken to the pier where they met with Hiro's friends since Baymax had contacted them to help Hiro's mood. While they all talked, Yokai appeared throwing crates at them and then they all got in Wasabi's car to escape. Hiro ordered Baymax to stay and attack, but Yokai easily knocked out the robot and made it plummet on top of the car. They were chased by the man throughout the city streets and almost got trapped by the Microbots, but ended up thrown to the bottom of the ocean, saved by Baymax while Yokai got away once more and believing they had drowned. Baymax managed to scan the man during the chase.

Hiro and the crew went to Fred's Mansion where they were greeted by Heathcliff. Inside, Hiro showed them a drawing of the Silent Sparrow symbol which he could spot when Yokai was carrying parts to build a machine. Fred suspected Mr. Krei was Yokai, but everyone doubted it, then Baymax revealed some of the health data that he obtained from his scan. With the information, Hiro realized they could scan the whole city at once with an upgrade and find Yokai.

By that time, Yokai had moved his operations to Akuma Island, the same place where the Silent Sparrow project took place and lost his daughter. Hiro made upgrades to Baymax's armor and gave his new friends and himself suits to apprehend the man. When Baymax found a match on Yokai's scan, the team was taken to the island where they found out the truth about the Silent Sparrow project, but still mistakenly believed Yokai to be Mr. Krei trying to bring back the project. Yokai then threw a block of cement at them and engaged the inexperienced team in a fight, easily defeating them, but losing his mask in the process.

Upon seeing Callaghan's face and learning he was the Yokai, Hiro became angered that Tadashi's sacrifice was for nothing. Callaghan told him it was his fault for going inside the building in the first place, and this made Hiro snap and take out Baymax's healthcare chip, turning him into a killing machine and ordered to take out Callaghan instead of arresting him. While being attacked by Baymax, Callaghan recovered the mask and got away as the rest of the team tried to stop Baymax and put the chip back on him. Later, the team was picked up by Heathcliff and showed Hiro more of the test's recording, revealing that the pilot was Callaghan's daughter and finally realized that Callaghan only wanted revenge for this.

Yokai moved his plans faster and attacked at Krei Tech Industries when Alistair Krei announced the inauguration of a new campus, using the Microbots to hold the Silent Sparrow's portal pieces together. The portal opened and slowly began sucking in all of Krei Tech until Big Hero 6 arrived and fought Callaghan once more. The team was caught again by Yokai's bots, but Hiro had them try different methods to break free. Learning from past mistakes, Hiro told them to attack the Microbots instead of trying to obtain the mask. The team did as they were told and so most of the Microbots were sucked into the portal until Yokai ran out of bots to utilize. Finally, Baymax took the mask and destroyed it, causing the remaining bots to stop and fall, dropping the portal as well. Baymax detected signs of life inside the closing portal and went inside with Hiro. Later, Hiro came out with a capsule containing Abigail Callaghan, but unfortunately, Baymax's body was left inside as the portal was shut, though he managed to give Hiro his healthcare chip. Callaghan was arrested while all this happened and could only look in sadness and disappointment at what he'd done.

After his arrest, the attack at Krei Tech was shown in the news, while everyone asked questions about the new heroes. The San Fransokyo Institute of Technology also had to look for a new dean, getting Professor Granville to replace Callaghan.

In "Mini-Max", Hiro visits Callaghan in prison to know more about Granville's past since he notices Granville has been doing things in secret. Callaghan reveals that many years ago there was an incident with Granville and one of her students. Although it was officially reported as a pipe burst, Callaghan heard rumors about it being an experiment gone wrong which made Granville resign.

Hiro sets to leave immediately after hearing what he wanted, but Callaghan stops him to thank him for having saved Abigail, then admitting fault for Tadashi's death and apologizing, though he knew it was not enough. Anguished, Hiro replies that forgiving him is what Tadashi would want him to do, but he is still not over it and hopes that he will someday be able to.

In "Hiro The Villain", Callaghan is interrogated by Chief Cruz about Big Hero 6. Callaghan only tells Chief Cruz that Big Hero 6 saved two lives, Krei and Abigail, and he's paying for his past unforgivable mistakes. When Chief Cruz mentions the fire incident at SFIT, Callaghan solemnly tells the chief that he's wrong about Big Hero 6.


  • Yokai - Yokai is the Japanese word for "spirit" or "phantom". Individually, the kanji used for the word is "bewitching" and "mystery". The term Yōkai can also refer to a class of supernatural spirits and monsters in Japanese folklore.


  • Callaghan's blood type is AB−.[1]
  • Yokai is the only character in the film with no apparent Marvel Comics counterpart, although he does bear a resemblance to Lord Deathstrike.
  • Despite being given the name "Yokai" in marketing, Callaghan is never actually referred to as such in the film. Yet, he is the only one to have a codename for his alter-ego, as the other superhero characters have nicknames for both their referred name and codename. He finally does get referred to as Yokai in Season 2 episode "Hiro The Villain", with it quite possibly being a moniker that the press gave him in the aftermath of his arrest rather than one he created for himself.
  • His name may have originally been Dr. Martin Lieber according to the 2013 Rotoscopers video and early information. As Lieber, he was not a big fan of Hiro's intelligence, though this may have been changed to prevent any dead giveaways to his identity.[3]
    • Interestingly enough, Stan Lee's birth name was Stanley Martin Lieber.



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