In the futuristic city of San Fransokyo during 2032, Hiro Hamada, a 14-year-old high school graduate and robotics prodigy, spends his time competing in illegal underground betting for robot fights. Hoping to get Hiro out of this dangerous lifestyle, his inventive older brother Tadashi takes him to the San Fransokyo Institute of Technology, where Hiro meets Tadashi's best friends: gritty Go Go Tomago, neurotic Wasabi, bubbly Honey Lemon, and comic book fan Fred. Tadashi also introduces his project, an inflatable AI healthcare robot named Baymax. After meeting Tadashi's mentor, Professor Robert Callaghan, Hiro applies to the university, impressing the school's showcase with his project: microbots that can link together into any configuration using a neural transmitter. Hiro and Baymax follow the microbot to an abandoned warehouse, where they discover the microbots being mass-produced by a Kabuki mask-wearing supervillain known as "Yokai". They narrowly escape and later track down Yokai, who is revealed to be Callaghan. Feeling betrayed by his friends' actions, Hiro leaves with Baymax, intent on avenging Tadashi.