Perhaps Kushina made a choice that Naruto felt was unfair to him. Like if she gave away something that was rightfully his, it could make him angry.
If Kushina was overly critical of Naruto in the fanfiction, always finding fault with him and not showing enough support, he would likely be angry. Naruto has always thrived on support from his friends and family, so a lack of it from his mother would be a big deal.
In a fanfiction, if Kushina was involved in something that led to the endangerment of Naruto's friends, he would be angry at her. Naruto values his friends highly, and any threat to them because of Kushina's actions would be unacceptable to him.
Naruto being angry at Kushina in fanfiction could stem from a feeling of abandonment. Even though she's his mother, if in the fanfiction she was absent during important moments in his life, whether physically or emotionally, Naruto could be angry. He might feel that she didn't fulfill her motherly duties. For instance, if she was more focused on other things like her own past traumas or relationships, and neglected Naruto's needs, that would surely make him angry.
One key element could be how the Saiyan traits are incorporated into Naruto. For example, his enhanced strength and fighting abilities. Also, the relationship between Naruto and Kushina could be explored in a new light, perhaps with some unique backstories or interactions based on the Saiyan concept. Another aspect could be how the Naruto universe is changed or affected by these Saiyan elements.
One possible reason could be some sort of dark influence or curse that makes her lose her maternal instincts. Maybe a powerful enemy targets her and in order to protect Naruto from further danger related to her, she feels forced to abandon him. Another reason might be that she is made to believe false information about Naruto, such as that he will bring great disaster to the village in the future.
One possible reason could be a mission. In many Naruto - related stories, missions often take characters away from their families. Naruto might have received a highly important and dangerous mission that requires him to be away from Kushina for a long time.
He could learn powerful sealing techniques. Kushina was known for her sealing skills, and she could pass them on to Naruto. This would give Naruto an advantage in battles and also in containing the Nine - Tails' power.
It could also be due to some external influence. Perhaps an enemy used some kind of mind - control or manipulation on Kushina. They made her think that Naruto was a threat, so she decided to disown him. In the Naruto universe, there are many powerful villains who could potentially do this kind of thing.
Maybe she's been possessed. In some fanfictions, characters can be taken over by dark forces. So Kushina could be under the control of some evil entity and that's why she hurts Naruto.
It could also be related to some hidden family secrets or prophecies. Maybe there was a prophecy that Naruto would bring great destruction in the future and Kushina, believing in it, thought she had to stop him before it was too late. This would be a very complex and heart - wrenching betrayal if it was based on such a false premonition.
Danzo could also be the one to make Naruto angry. Danzo's underhanded tactics and secrets might be exposed in the fanfiction, and if they were to directly harm Naruto's friends or the village, Naruto would be furious at his actions.
Maybe in the fanfiction, if someone on the Argo 2 endangered his friends, Percy would get angry. He's very protective of his friends, like Annabeth. If any harm came their way because of someone's recklessness on the ship, that could set him off.