Well, some characters might be amused. For example, Atsushi could be a bit shocked at first, seeing the different interpretations of Dazai in the fanfiction. He might find some of the more out - there scenarios quite strange but also interesting in a way.
It gives fans a chance to explore different 'what - if' scenarios. By seeing the Avengers' reactions, fans can get a deeper understanding of the characters.
Some fans might be disappointed. Fanfiction often allows them to explore different scenarios with Naruto's character. If he gives it up, it's like closing a door on those creative possibilities.
The Naruto fandom would likely be very divided. Some fans would be extremely outraged as it goes against the core values and character of Naruto. They might condemn such a fanfiction.
On the other hand, there would be fans who would welcome it. Maybe they never liked the pairing in the first place or they think it adds an interesting twist to the story. They could start exploring new relationships for both Sasuke and Sakura in their own fan - created stories.
The Naruto fandom would probably react very negatively. Fans are used to seeing Naruto as a hero, a symbol of hope and growth. A fanfic that portrays him as a slave goes against the very essence of what Naruto represents. There would be a lot of criticism on social media platforms, and many fans might even call for the fanfic to be removed or boycotted.
Dazai is not based on a true story. Usually, characters like Dazai are formed through the author's imagination and artistic expression to create an engaging narrative for the readers.