He might use sign language. If there are other characters in the fanfiction who know sign language, they can act as interpreters for him. For example, Lucy could have learned sign language to be able to communicate with Natsu better.
One possible reason could be a past trauma. Maybe he witnessed something really horrible during a battle or an incident at school that shocked him so much he lost his ability to speak. For example, if he saw a friend in great danger and was powerless to help immediately, it could have had such a psychological impact on him.
He might initially be shocked and confused. Natsu has always been so loyal to Fairy Tail, so this would be a huge blow to him.
In many fanfictions, Natsu protects Lucy by using his powerful fire magic against their enemies. For example, if they encounter a dark guild attacking Lucy, Natsu would jump in front of her and unleash a flurry of fire attacks like his 'Fire Dragon's Roar' to drive the enemies away.
In some fanfictions, Natsu might save Lisanna from a powerful dark wizard. He could use his Fire Dragon Slayer magic to overpower the enemy and rescue her.
In some fanfictions, Lucy might use her Celestial Spirit magic. For example, she could summon a powerful spirit like Leo to help fight off whatever is threatening Natsu. The spirit could provide a distraction or directly combat the enemy while Lucy tries to reach Natsu and get him to safety.
He might initially be in disbelief. Natsu is used to the loyalty among his Fairy Tail comrades, so betrayal would be a shock to him.
The Natsu and Gray gay fanfictions contribute to the Fairy Tail fandom by providing a creative outlet for fans. It allows fans to express their love for the characters in a different way. Since the Fairy Tail series already has a large and passionate fan base, these fanfictions can bring together like - minded fans who enjoy this particular aspect of the characters' relationship. It can also lead to fan - made art, discussions, and even collaborative projects within the fandom, all of which help to keep the Fairy Tail community alive and vibrant.
Natsu would likely be extremely hurt. He has always been loyal to Fairy Tail, so being betrayed would be a huge blow. He might initially be in disbelief, not wanting to accept that his friends and guildmates could turn on him.
If Natsu is a girl in this fanfiction, her character might change in terms of her relationships. For instance, she may be more self - conscious about her appearance compared to when she was male. Also, her interactions with male characters like Gray could shift. Instead of their typical rival - like banter, there could be a more complex emotional undertone, like a friendly - rivalry with a hint of romantic tension perhaps.
Maybe Natsu hates Fairy Tail fanfiction because he doesn't like how some fanfictions distort the original story or the characters. In the original Fairy Tail, he has a clear personality and relationships, and fanfictions might change that in ways he wouldn't like.