Set five years after the Big Hero 6, the team are now established superheroes in the city. But now an army of mutants led by a psychopathic super villain threatens to tear their city apart. While this happens, GoGo realises that she needs to address the fact that Hiro is no longer a child.

After GoGo gets into an accident, Hiro learns her family is unable to pay the medical bills. Though when he becomes determined to do "anything" to help, he realizes that anything can be worse than he imagined. Contains Hiro x GoGo Please Review.