The villains would have diverse reactions too. Garou might see the fanfic as a source of inspiration for his own 'evil' plans. He might think that some of the ideas in the fanfic could make him an even more formidable foe. However, if the fanfic makes him look like a complete fool, he'd be enraged. Deep Sea King would be confused by the fanfic, not really understanding the concepts that are different from his simple view of the world. But he might also be intrigued by the new versions of himself presented in the fanfic.
When it comes to Genos' abilities, the Avengers would be intrigued. Genos' ability to fire intense energy blasts could be a great asset in battles. Hawkeye might be thinking about how Genos could provide cover fire or take out tough enemies from a distance. But the Avengers would also be a bit worried about Genos' lack of emotional control at times. In his pursuit of power and revenge, he can be a bit reckless. The Avengers would need to work with him to make sure he doesn't go overboard. Also, Genos' loyalty to Saitama would be something they would need to understand, as it might influence his decisions within the team.
They would probably have a range of reactions. Some might be excited to see a different take on heroism. Others might be skeptical. For instance, Todoroki could be interested in how the characters in One Punch Man deal with their powers compared to how he deals with his quirk.
The villains would have a mixed reaction. Some of the more power - hungry ones might see this as an opportunity to join forces with Saitama and cause even more chaos. However, there would also be villains who are afraid of Saitama's power, even if he's on their side now. They would be worried that he could turn on them at any moment. Overall, Saitama turning evil would completely disrupt the existing power dynamics in the One Punch Man world.
They might immediately stop the concert. The members would be really worried. For example, Jin could rush over to where Y N is with a concerned look on his face. He might ask the medical staff what's wrong and offer words of comfort.
Yes, there likely is. The Naruto and One Punch Man fandoms are both quite large, and it's common for fans to create crossover fanfictions. These crossovers can be really interesting as they combine the unique elements of both universes, like Naruto's ninja skills with Saitama's one - punch power.
I'm quite sure there exists a 'Naruto is One Punch Man' fanfic. The world of fanfiction is vast and full of all kinds of creative crossovers. Writers might be intrigued by the idea of bringing Naruto's ninja skills and the unique world of One Punch Man together. For example, how would Naruto react to the overpowered villains in One Punch Man's world? And how would Saitama view Naruto's determination to protect his village? These are the kind of things that could be explored in such a fanfic.