Naruto's friends from Konoha would likely be very supportive. Kakashi might offer some wise words about the responsibilities of parenthood. Sakura would probably be there to help with any medical concerns Mirajane might have during the pregnancy. As for Mirajane's friends from Fairy Tail, they would be excited. Erza would be making sure Mirajane is well - protected and would probably train Naruto a bit to make sure he can defend his family. Gray might make some jokes to lighten the mood but also be ready to help out.
Well, there could be such a fanfiction out there. However, it really depends on the creativity and interests of the fanfiction writers in the relevant fandom. Some might find this concept interesting to write about, while others may not. It also might not be very common as it involves a rather specific and perhaps controversial plot point in the context of the characters.
One possible plot twist could be that there is some sort of magic or jutsu involved that endangers the pregnancy. For example, a dark magic user might target Mirajane because of her unique powers and the fact that she is pregnant, seeing the unborn child as a potential threat in the future. Another twist could be that Naruto discovers a new form of chakra that can only be accessed through the combined efforts of him and Mirajane during her pregnancy, which then becomes crucial for saving their world from a great evil.
In most Naruto fanfictions, Mirajane is from the Fairy Tail universe and Naruto is from the Naruto universe. They exist in different fictional worlds, so the idea of Mirajane 'cheating on' Naruto doesn't really make sense in the context of traditional fanfiction. However, if it's some kind of crossover fanfiction with a really strange and out - of - the - box plot, it would be very rare and not a common trope.
One possible fanfiction could be about Naruto visiting the Fairy Tail world and teaming up with Erza and Mirajane. They could go on a quest together to defeat a powerful dark wizard. Naruto's unique ninja skills would blend well with Erza's swordsmanship and Mirajane's takeover magic.
They could start by meeting in a strange, in - between world. Naruto is intrigued by Erza's armor and Mirajane's different forms. They soon realize they have a common goal, which is to find a way back to their own worlds. As they journey, they share stories of their past adventures, with Naruto talking about his battles in the Hidden Leaf Village and Erza and Mirajane sharing tales from Fairy Tail.
One possible fanfiction could be about Naruto ending up in the Fairy Tail world and teaming up with Erza and Mirajane. They could go on adventures together, with Naruto's unique ninja skills complementing the magic of Erza and Mirajane. For example, Naruto's shadow clone jutsu could be used in creative ways during battles against powerful foes in the Fairy Tail universe.
Another option is to check out some Fairy Tail - focused fan communities on social media platforms such as Reddit or Tumblr. Sometimes, fans share links to interesting fanfictions in these communities. However, make sure to follow the community rules when looking for such content.
I'm not entirely sure if there is a specific 'natsu and mirajane pregnant fanfic'. Fanfic availability can vary greatly. Some fanfic authors might have explored this idea, while others may not. You could also try reaching out to fanfic communities on social media platforms and ask if anyone knows of such a fanfic.
In a Naruto - Fairy Tail - Mirajane fanfiction, it could start with Mirajane traveling to the Naruto universe. She might be on a quest to find a special kind of magic that she believes exists there. When she arrives, she meets Naruto. Naruto, being the friendly and curious person he is, offers to help her. They then explore the ninja world together, with Mirajane learning about ninjutsu and Naruto learning about Fairy Tail magic.