Naruto's friends in Konoha would probably be a bit surprised at first. But they would soon come around and support him. His old mentor, like Iruka, would be happy for him. As for Mei's side in Kirigakure, her comrades might be a bit more cautious. But once they see how Naruto can contribute to their village as well, they would accept the relationship.
If RWBY were to react to Spy x Family fanfiction, they would bring their own perspectives. Ruby, with her innocent and curious nature, would likely be intrigued by Anya's telepathic abilities. Weiss, being more refined, might analyze the political and social aspects of the Spy x Family world. Blake, having experienced secrecy herself, would empathize with the characters hiding their true identities. Yang would enjoy the comical moments and the action - packed sequences, like when Loid does his spy stunts.
Gray would be extremely angry. He would immediately start looking for clues as to where Natsu was taken. His ice - make magic would be on full display as he might freeze things in frustration while trying to figure out the situation.
For Peter Parker's family, the news of his marriage to Scream would be quite a bombshell. Aunt May would likely question Peter's judgment. She might think that Peter is getting in over his head and that Scream is not the right person for him. But Peter would defend his relationship, saying that Scream has a good heart beneath her tough exterior. Regarding Scream's family, if they are part of a more villainous group, they might try to break up the marriage. But if they are more open - minded, they could see the potential in Peter and support the relationship. The reactions of their families would add a lot of drama and conflict to the fanfiction.
Tails would probably be very helpful. He'd use his intelligence to make sure Amy has a comfortable pregnancy, like creating special devices for her. Knuckles might be a bit awkward at first but would ultimately be very protective. He'd stand guard to make sure no harm comes to Amy and the unborn baby.
If the My Hero Academia characters were to react to Spy x Family fanfiction, it would be quite a spectacle. Momo Yaoyorozu could be impressed by the creative plots in the fanfiction. She might admire how the Spy x Family world is built with its own set of rules and characters. Kirishima would likely be excited by the action scenes. He'd be all about the times when Loid has to fight or use his spy skills. And Mineta? Well, he might have some inappropriate thoughts, but we'll just ignore that and focus on the more positive reactions of the other characters.
Beast Boy would be quite distraught. He might initially feel a bit helpless, but then he'd start thinking of creative ways to find Robin. He could transform into various animals to search for clues or to sneak into Red X's lair. His sense of humor might also help to keep the team's spirits up during the search, even though they're all worried about Robin.
Peter would probably be shocked at first. He's used to dealing with super - villains and saving the city, not impending fatherhood. But then he would likely step up and be very protective. He'd make sure Jean had the best medical care and start thinking about how to keep their home safe from any threats.