Regarding the relationship with other characters, Kakashi's overprotectiveness of Sakura can strain relationships. For example, the other ninja in the village may think Kakashi is playing favorites, which could lead to resentment among some. With their own teammates, it can be a bit of a mess. Naruto might try to understand at first but as time goes on, he may get frustrated that Kakashi seems to be only concerned with Sakura's safety. Sasuke may view it as a sign that Sakura is not as strong as she claims and this could further damage their already complex relationship.
It can make other characters view their relationship as very exclusive. For example, Ron might feel left out sometimes if Harry is constantly overprotective of Hermione. This can create some tension between Ron and Harry in the fanfiction.
It could make his relationship with Naruto tense. Naruto might notice Kakashi's special attention to Sakura and feel jealous or confused. After all, Naruto also cares a great deal about Sakura. And with Sasuke, Kakashi's obsession could make Sasuke distrust him more, as Sasuke is also connected to Sakura in his own way.
It can speed up their relationship development. His overprotectiveness shows his feelings for her, and Hinata may feel more secure and cared for. This can lead to her opening up more to Naruto and their relationship becoming closer faster.
Well, it really depends on how the author writes it. If the overprotectiveness is written in a way that respects Marinette's agency, it could be a cute and endearing aspect of their relationship. But if it comes across as controlling, it might make Marinette resent Adrien, and then they would have to work through those issues to have a healthy relationship.
It might initially make Percy feel smothered. He's used to being independent, and having Artemis constantly hovering could make him a bit resentful. But on the other hand, it could also make him feel safe. Given that he's 'broken', having someone so powerful care about his well - being could start to heal some of his emotional wounds.
It can limit Percy's growth as a character. If Artemis is always protecting him, he might not get to face challenges on his own and develop fully. Other characters might feel sidelined because Artemis is so focused on Percy. For example, some of Percy's friends who also want to help him might find it hard to get involved if Artemis is constantly stepping in.
Clarise's overprotectiveness can affect the relationships in the story. It could strain her relationships with other characters who don't approve of her actions. At the same time, it might strengthen her bond with Percy, either in a positive way if he appreciates it, or in a negative way if he feels smothered. This complex web of relationships influenced by her overprotectiveness can drive the story forward in many different and unexpected ways.
In this fanfiction scenario, Kakashi's failure might cause Sasuke to be more reckless. Sasuke, feeling let down, could go off on his own more often. Sakura, who might have relied on Kakashi to keep Sasuke in check, would then be left to try and deal with Sasuke on her own. This could put a lot of stress on their relationship. She might be more desperate to bring Sasuke back to the right path, but Sasuke could see her as being too pushy, all because of Kakashi's initial failure.
However, this conflict could also be a turning point in their relationship. As Naruto gets mad, he might voice out his true feelings. Kakashi, in turn, could then explain his actions better. This could lead to a deeper understanding between them in the long run. For instance, Kakashi could finally reveal some secrets about his past training methods that Naruto didn't know before, which could make Naruto respect him more.
It can add a lot of tension to the story. For example, Naruto might feel suffocated by Minato's overprotectiveness and constantly try to break free. This can create a conflict between them. Also, it can limit Naruto's growth as a character in some ways. If Minato is always shielding her from danger, she might not get the chance to fully develop her skills and become stronger on her own.