One possible reason could be betrayal. If her friends, say Ron or Harry, were to lie to her about something really important, like a secret mission or a hidden danger, that would make Hermione furious. In fanfiction, her loyalty to her friends is often a central part of her character, and any threat to that trust could lead to her anger.
It might be discrimination. If in the fanfiction world there is any form of discrimination against Muggle - borns, like Hermione, she would be furious. She has always been proud of her Muggle - born heritage and would fight against any form of unfair treatment towards those like her.
Another reason could be related to school work. If there are new rules in Hogwarts that she deems unfair regarding academics, like restrictions on library access or new grading systems that don't reward hard work properly. Hermione is all about learning and fairness in education, so this could really make her angry.
One possible reason could be a disagreement over how Molly treats Harry. Maybe Molly is being overprotective of Harry in a way that Hermione thinks is hindering Harry's growth as a wizard. For example, if Molly tries to stop Harry from taking certain risks that Hermione believes are necessary for his development.
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.
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.
If the gods were to interfere with her plans for the hunters without her consent. Artemis is very protective of her hunters and their way of life. Any meddling from the other gods in her domain could easily enrage her in a fanfiction scenario.
Another reason could be a dangerous situation they find themselves in. Maybe they are in a dark and spooky part of the Forbidden Forest, and Draco makes a sudden movement or noise that scares Hermione. Fanfictions often explore tense and thrilling scenarios where the characters' reactions, like Hermione's shriek, add to the drama.
Maybe Hermione made a decision regarding Ron that Mrs Weasley didn't approve of. For example, if she rejected Ron's marriage proposal in a rather harsh way, Mrs Weasley, who was very fond of Hermione as a potential daughter - in - law, could be extremely disappointed and angry.
When magic is misused. Hermione is very much by - the - book when it comes to magic. If she sees someone using dark magic or even just misusing a simple spell in a dangerous way, she'll be angry. For example, if a fellow student tries to use an untested charm on another student just for fun and it goes wrong.
Hermione's intelligence is a key quality. It allows for all kinds of interesting plotlines where she uses her knowledge to solve problems, whether it's in a school setting like at Hogwarts or in the wider wizarding world. For example, she could be the one to figure out a complex magical mystery that no one else can.
One possible reason could be that she feels misunderstood at home. In the wizarding world, Hermione is a very intelligent and studious witch. If her family doesn't understand or support her magical pursuits, she might feel the urge to run away. For example, if they constantly tell her to focus more on 'normal' things and less on her spells and potions, it could drive her away.