A fanfiction idea could be that Thor becomes overprotective of Loki when they are on a mission off - world. Loki is trying to use his skills to gather information but is in a dangerous area. Thor follows him closely, ready to fight off any threats. He might even go as far as to not let Loki out of his sight for a moment. This overprotectiveness could stem from Thor's love for his brother and his newfound understanding of Loki's importance in his life, as well as in the grand scheme of things in the Avengers universe.
One manifestation is that they are quick to correct any inaccuracies in the fanfic regarding the Naruto lore. For example, if a fanfic writer gets a character's backstory wrong, fans will point it out immediately. Another is that they may be very critical of any fanfic that seems to go against the core values of Naruto, such as a story that promotes excessive violence without any good reason when Naruto is all about positive values.
One sign is that Arthur always keeps Merlin close by his side. He doesn't let Merlin take on overly dangerous tasks alone. For example, if there's a mission to a dangerous place, he'll either go with Merlin or send a lot of guards with him.
One possible fanfiction could be where Ruby is overprotective of her team during a dangerous mission. Maybe she constantly checks on their safety, making sure they don't take unnecessary risks. For example, when they are facing Grimm, she might be extra vigilant about any threats towards Weiss, Blake, and Yang, and jump in to protect them even before they realize the danger.
It could be that Percy has a special connection to one of the major gods. For example, if he's related in some way to Zeus or Poseidon, the other gods would be extra careful with him. Also, Percy might have done something in the past that made the gods feel indebted to him, and this overprotectiveness is their way of repaying him.
I really like the fanfic 'Overprotective Sasuke'. In it, Sasuke's overprotectiveness towards Sakura is a result of his fear of losing her again. After all they've been through, he just can't bear the thought of her getting hurt. It's filled with sweet moments where he'll glare at anyone who gets too close to her in a menacing way. And there's also a great deal of character development for both of them as they navigate their relationship with this new dynamic.
Well, it changes their relationship in that they become closer. Dudley's overprotective nature means he starts to see Harry as someone precious to him. This could lead to them sharing secrets. Harry might tell Dudley more about the wizarding world, and Dudley could confide in Harry about his insecurities. They might even team up against common enemies, like those who look down on both of them for different reasons. Overall, it makes their relationship more complex and interesting.
One possible plotline could be Naruto protecting his younger sibling from the threats of rogue ninjas. He would use his skills and influence in the ninja world to keep them safe, perhaps even training them secretly to ensure they can defend themselves. Another plotline might involve Naruto dealing with a political situation where his sibling is in danger due to their relation to him. He has to navigate the complex world of ninja politics to safeguard his family.
One possible plot could be that during a dangerous mission, Team 7 - Naruto, Sasuke, and Kakashi - constantly shield Sakura from every possible threat. For example, Naruto uses his shadow clones to form a protective barrier around her at the first sign of danger. Sasuke is always on high alert and uses his Sharingan to detect any hidden enemies that might target Sakura. And Kakashi steps in with his vast experience to make sure no harm comes to her.
A great fanfiction example could be set during a festival in the village. Hinata is excited to participate in a traditional dance, but Naruto is worried she might get hurt in the crowded area. So he stays really close to her, almost like a bodyguard. He scares off any guys who look at Hinata a bit too long. Another aspect could be in a training session where Hinata is paired with a tough opponent. Naruto is so overprotective that he tries to interfere in the training, thinking the opponent is being too rough. This causes some tension between Naruto and Hinata at first, but eventually they work it out and their relationship grows stronger.