Hiro and his friends discover that Karmi has been writing fan-fiction about them. Everyone, especially Fred, are impressed as well flattered by Karmi's stories. Hiro on the other hand feels embarrassed because Karmi has depicted him as her boyfriend. Meanwhile, master thief and sushi chef, Momakase, escapes from prison with help from Obake. Hiro and Baymax, who are out on night patrol, pursue her, but lose her in an alley when one of Obake's drones intervene. She later arrives at Obake's hideout, and confronts him for his reasons for breaking her out. As both agree that they have a common enemy in Big Hero 6, Obake proposes an alliance to eliminate their mutual foe. Momakase accepts and is given a scan-jammer to prevent Big Hero 6 from locating her.
Since Baymax is unable to scan for Momakase due to the jammer, Wasabi suggests scanning for her graphene blades, as graphene conducts heat. It works, and Big Hero 6 track Momakase to Securitech. They arrive too late. Momakase had just left, and was now on the run. Go Go chases after her. She soon catches up, but loses her when she scales the buildings and jumps onto the rooftops. However, Go Go has a go a trying a move called "veloci-shot" from Karmi's stories. She backs up a bit to build up some acceleration. Down on all fours, she charges towards the wall ahead at sonic speed. She jumps and skates vertically up the wall, making it to the rooftops. Go Go then continues the chase and soon catches up with Momakase. She engages her in a brief fight, but Momakase gets away after she slices through Go Go's discs. Back at Securitech, the rest of the team discover that Momakase has stolen everything the company has been working on. For what reason, they have yet to find out.
Meanwhile, in school, Karmi's Big Hero 6 fan-fiction has become so popular that its the only thing everyone at SFIT talks about. Everywhere Hiro goes, people are talking about Karmi's latest chapter and the relationship between Karmi and "Captain Cutie". All the while Hiro gets more and more irritated. He finally decides to try and get Karmi to stop writing fan-fiction. However, on the night when she is supposed to leave the bio-lab, Big Hero 6 receive a message from Momakase. She has kidnapped Karmi and threatens to harm her unless they meet her at Krei's old lab on Akuma Island, which is scheduled for demolition. Big Hero 6 arrive on Akuma Island and split up into three teams. One by one, Momakase captures Wasabi, Fred, Honey Lemon and Go Go. Hiro and Baymax find Karmi, too late to realise they have fallen into a trap. Momakase traps them in a Big Hero 6 proof cage, along with Karmi and the rest of the team. Before leaving them to their fate, she tells them that a disintegration device has been planted and set to wipe out everything on the island.
Trapped in a cage that has been specially designed to contain, Big Hero 6 see no chance of escape. Hiro on the other hand reveals that he has upgraded Baymax with an overdrive mode, inspired from Karmi's stories. Baymax transforms into a superpower robot, and uses an energy sword to break through the bars, freeing them. However, using overdrive mode has drained Baymax's battery, rendering him useless to fly everyone out. Big Hero 6 and Karmi head for the shore as an energy shock wave builds up. Working together, like in Karmi's stories, Fred and Honey Lemon create an ice slide. They escape the island on a block of ice just as the shock wave disintegrates everything on the island. Karmi is thankful for them coming to her rescue, and surprised that Hiro built an actual overdrive mode into Baymax. In a way, it was Karmi who helped Big Hero 6 save the day. Hiro was going to criticize Karmi for her fan-fiction, but, unable to hurt her feelings, commended her. Karmi then wrote the next chapter of her fan-fiction, which involved herself and "Captain Cutie" kissing, much more to Hiro's embarrassment.
- Ryan Potter as Hiro Hamada, Student #3
- Scott Adsit as Baymax
- Génesis Rodríguez as Honey Lemon
- Khary Payton as Wasabi, Student #2, Backwards Cap
- Jamie Chung as Go Go Tomago, Student #5
- Brooks Wheelan as Fred, Student #4
- Haley Tju as Karmi, Student #1
- Naoko Mori as Momakase
- Andrew Scott as Obake
- Diedrich Bader as Bluff Dunder, Robotic Voice
- The fantasy sequence references several anime traits. Big Hero 6 are portrayed in Chibi style, the characters give off anime shocked faces, and Baymax's transformation references similar sequences seen in anime.
- This episode noticeably addresses the fact that the Big Hero 6 do not have alternate code names for themselves, with the exception of Fred who has taken the name "Fredzilla". The reason for this is because their given nicknames were their code names in the comics, Fredzilla included.
- The title is a pun on "fan fiction", which means characters or settings from original work of fiction being written by fans of their own work rather than by their creators.
- It also benefits on Karmi writing her fan-fiction on Big Hero 6.
- Hiro's Megabot appears in his locker at SFIT.