One possible event could be that Kurenai accidentally endangers one of Naruto's loved ones during a mission. This would make Naruto angry at her.
Maybe Kurenai takes a side against Naruto in a village dispute in the fanfic. She might support a decision that Naruto believes is wrong for the village, causing him to hate her.
Maybe in the fanfic, Kurenai has some actions that conflict with Naruto's beliefs. For example, she might oppose Naruto's way of handling certain village matters.
A plot could also be centered around Naruto asking Kurenai out on a date. He would be really nervous and might ask for help from his friends. His friends could give him all kinds of advice, some good and some really bad. And when he finally does ask her, Kurenai's reaction could be a mix of surprise and amusement. This could lead to a series of events where they get to know each other better on this 'date' and explore their relationship further.
In a Naruto Kurenai pregnant fanfic, the plot could focus on the medical aspects as well. Given the unique world of Naruto with its own medical ninjutsu, it could show how the village's medical team takes care of Kurenai during her pregnancy. Maybe there are some complications that only the special ninja medicine can solve. Additionally, the plot could involve Kurenai training in a different way during her pregnancy to keep her skills sharp but also be safe for the baby. This could lead to her developing new techniques or modifying her old ones. And of course, there could be a sub - plot about the other characters' anticipation of the new addition to the village.
It's possible that in the fanfiction, the Cullens are involved in some sort of betrayal. For example, they might side with someone who is against Bella. This act of betrayal would be a strong reason for her to hate them. In fanfiction, new storylines can be created where the Cullens' actions are not in line with what Bella expects or desires, which can result in her hatred.
In the fanfic, it could be that Kami has a conflict with one of Naruto's allies, and Kami's actions against that ally make Naruto angry and lead to his hatred. For example, if Kami tries to punish Naruto's friend for no good reason, Naruto would not be happy with Kami at all.
Perhaps he thinks fanfic undermines the integrity of the original Naruto story. The official story has a certain narrative and character development, and fanfic can deviate from that significantly. When it comes to his connection with Naruto, any deviation in fanfic might be seen as a negative. For example, if a fanfic changes the way he mentors Naruto, it could be something he wouldn't like.
One possible event could be that the Yondaime in the fanfiction is revealed to have faked his death and left Naruto on purpose to face hardships alone. This would make Naruto feel betrayed and lead to hatred.
The power scaling might be another issue. Naruto has a very detailed and complex power system that is based on chakra, jutsu, and ninja ranks. Fairy Tail has its own magic - based power system. In fanfics, getting these power systems to mesh well can be difficult, and Naruto might 'hate' being part of a poorly - balanced power - system fanfic.
Another reason could be that the Rookie Nine have different goals or values that conflict with Naruto's. For instance, if they are more focused on self - interest rather than the greater good that Naruto is always striving for. This divergence in values might lead to Naruto's dislike and eventually hatred for them. And also, personal conflicts within the group that Naruto gets caught in the middle of could be a factor.
Well, perhaps in this fanfic, the pregnancy could be a result of a special mission or some sort of magic that binds Kurenai to a character. And Naruto, being the hero he is, gets involved to help Kurenai understand and deal with the situation. He could also help her face the reactions of the village, which might be mixed since Kurenai is a respected shinobi.