The Fairy Tail guild would probably be very curious about Naruto at first. They might be amazed by his strange abilities like running up walls and creating clones. Some members, like Lucy, would likely be a bit cautious, but also intrigued. Natsu would probably be eager to test his strength against Naruto right away.
The guild as a whole would likely mobilize. Erza would start formulating a strategic plan. She'd consider the strengths and weaknesses of Acnologia and figure out the best way to approach the situation. Gray would also be ready to fight, using his ice - make magic to support the rescue mission. They would all be united in their determination to get Lucy back safely.
Fairy Tail would be a mix of reactions. The younger members would be thrilled and look up to Naruto as a hero. The older and more experienced members would assess his skills and how he could fit into the guild. They might also be a bit protective of their way of life in the guild at first, but as they get to know Naruto better, they would accept him as one of their own.
Naruto would likely be very confused at first. He has a strong sense of belonging and has always fought for his place in his own ninja village, so being suddenly banished from the Fairy Tail guild would be a shock. He might try to plead his case and explain that he has done nothing wrong.
It could lead to a change in the guild's dynamics. Naruto has his own unique combat style and abilities. His departure might make the guild realize the need to diversify their fighting strategies. For example, they might start to look for members with skills similar to Naruto's ninja techniques.
The guild would likely be shocked at first. They consider Natsu as one of their own, so his attack would be completely unexpected. Some members might try to talk him down, like Lucy. She has a close bond with Natsu and would probably try to reason with him.
One possible fanfiction could be about a character from Naruto being transported to the Fairy Tail universe and getting involved with a Dark Guild. Maybe Naruto's skills in combat and his never - give - up attitude would help him either infiltrate the Dark Guild to gather information for Fairy Tail or try to reform some of the members.
The guild members' reactions would vary greatly. Happy, being Natsu's closest companion, would likely be excited about the fanfiction. He might fly around the guild hall, telling everyone about it and adding his own little comments about how accurate or inaccurate it is. He would definitely be protective of Natsu's image in the fanfiction, especially if it's not a positive portrayal.
At first, they might be in disbelief. The members of Fairy Tail see Natsu as a core part of the guild, so it would be hard for them to accept that he has betrayed them. They would probably try to talk to him and find out what's going on. Some members might be angry immediately, thinking that he has turned his back on their family. But others, like Lucy, might be more hesitant to believe it and would look for a way to resolve the situation without conflict.
The guild would likely be ecstatic. Gray would probably make some snarky comment about Natsu finally growing up, but deep down he'd be happy for his friend. Erza would be all for it and might start planning the wedding immediately, giving orders to everyone in the guild to help out.
Some members might be initially cautious. Given her past as a powerful and somewhat feared being, they would be worried about her true intentions. For example, Gray might be on guard until he sees her actions are genuine.