The guild's reaction would be complex. Gray, for instance, would be both angry and confused. He and Natsu have a love - hate relationship, but they are still comrades. He might initially try to fight back, but then realize something is wrong. Erza would probably be more composed. She would try to assess the situation quickly and find a way to stop Natsu without causing too much harm, as she is one of the strongest and most level - headed members of Fairy Tail.
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.
When Natsu attacks Fairy Tail in fanfiction, the guild's reaction would vary among its members. Happy, Natsu's closest friend, would be heartbroken. He would try his best to snap Natsu out of it, flying around him and shouting. Makarov, the guild master, would be deeply saddened but also determined to resolve the situation. He might use his magic to restrain Natsu while trying to figure out what has caused this sudden change. And the younger members of the guild would be terrified, looking up to the older ones to handle the situation and protect them.
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.
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.
One possible motive could be that he's been mind - controlled. There are many villains in the Fairy Tail universe who have the ability to control others. Another reason might be a misunderstanding. Maybe he thought Fairy Tail had betrayed him in some way. It could also be a result of some dark magic that has affected his judgment.
Emotionally, Natsu could become more empathetic. If he meets characters in the dark guild who had a difficult past that led them to the dark side, he might start to see things from their perspective. This doesn't mean he would support their actions, but he would understand them better. For example, if there's a character in the dark guild who was orphaned and turned to dark magic for survival, Natsu might feel sympathy for them and try to offer an alternative path rather than just attacking them. This would show a more mature and compassionate side of his character that wasn't as prominent before.
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.
She would fit in very well. The Fairy Tail guild is all about family and acceptance. Given her parents are Lucy and Natsu, she'd be welcomed with open arms. She could learn from the older members like Makarov and Mirajane, and bond with the younger ones like Romeo. Her magic skills would also contribute to the guild's strength during battles or when helping the town.
He could leave because of a misunderstanding. Maybe he overhears something wrong and thinks the guild doesn't trust him or value him anymore. So in a fit of anger and pride, he decides to leave.
One possibility could be that Natsu is under some sort of dark magic influence. Maybe a powerful enemy has managed to control his mind, making him turn against the guild master. Another reason could be a misunderstanding. If some false information is fed to Natsu about the guild master being a threat to the guild or his friends, his hot - headed nature might lead him to take drastic action without fully understanding the situation.
Natsu would be heartbroken. Fairy Tail is like his family. He'd probably go on a solo journey to clear his name and prove his loyalty. Erza would be stoic but deeply hurt. She'd start an investigation within the guild, using her influence and intelligence to uncover the truth. She might also isolate herself a bit while she figures things out.
Gray would be shocked at first. He and Natsu have a long - standing rivalry - but also a deep friendship. He might initially be angry that Natsu would just leave like that, but then he would realize how much he'll miss him. He might also feel a sense of loss for the guild as a whole, since Natsu is such an important part of it.