The guild would be devastated. Natsu would probably be one of the first to be enraged. He'd vow to find whoever or whatever was responsible and make them pay. His fire would burn hotter than ever as he channels his anger.
Erza might be shocked. After all, Naruto is an important part of her life in the fanfiction. She could initially try to convince him to stay, using her own experiences in Fairy Tail to persuade him.
Some of their friends might be worried at first. They know the dangerous lives that Natsu and Erza lead. But then, they would all come around and be very supportive. They could throw a big celebration for the pregnancy, and everyone would chip in to help make a comfortable space for the baby in the guild. There would be a sense of new hope and family spirit in the group.
The guild master, Makarov, would be very protective. He'd see it as his duty to keep baby Erza safe. He might assign different members of the guild specific tasks like getting baby supplies or researching spells. Juvia would be over - the - top in her care for baby Erza. She'd constantly be fussing over her, making sure she's warm, clean and happy.
Natsu might be initially shocked and confused. He's not the type to expect rejection, so he could be at a loss for words at first. For instance, he might just stand there with his mouth open, not believing what he just heard.
Naruto would probably be extremely hurt. He is someone who values friendship and trust deeply. So, he might initially be in shock and disbelief. He would likely feel angry too, but his anger might be mixed with sadness.
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.
Natsu would probably be really excited. He'd be looking forward to having a new little friend to play with and might even start thinking up crazy names for the baby. Lucy would be very supportive, offering Erza advice on pregnancy and motherhood, perhaps sharing some of her own experiences or knowledge from books she's read.
He may try to understand Erza's reasons. Natsu, despite his impulsive nature, has a big heart. He might respect Erza's decision and step back, trying to keep their friendship intact. However, he could also be a bit persistent in a non - annoying way. He might keep showing his care for her in a more friendly manner, hoping that over time, she might change her mind.
Their friends would be overjoyed. Lucy would probably be the first to offer babysitting services. Gray might act all cool about it, but secretly be really excited for them. Happy, being Natsu's partner, would be super thrilled and would constantly be flying around the baby, making it laugh. Makarov would be like a proud grandfather, giving advice on how to raise the child in the Fairy Tail way.