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.
Another scenario could be in social situations. Maybe at school, when other students interact with Marinette in a way that Adrien deems inappropriate or potentially harmful, he steps in and is overprotective. For example, if a boy flirts with Marinette a bit too much, Adrien might get very defensive.
Well, it could strengthen their relationship. Adrien, as Chat Noir, has always been in a similar situation. So he can really understand what Marinette is going through. They might start to rely on each other more and share their experiences of having a double life.
Well, it could be a bit rocky at first. Adrien might be in disbelief and not know how to act around Marinette. But as time goes on, he could start to see all the times Marinette has shown the same qualities as Ladybug, like her courage and kindness. This realization would slowly bring them closer. For example, he might remember all the times Marinette has stood up to bullies at school, just like Ladybug does against villains. Eventually, they would have a deeper, more meaningful relationship.
It often drives the plot in interesting ways. Erza's overprotective nature can lead to her making decisions that Natsu disagrees with. This causes a rift between them that needs to be resolved. As they work through their differences, the story progresses. Also, it can attract the attention of other characters who either support or oppose Erza's actions, further complicating the plot.
The kittens can act as a catalyst for their relationship. As they play with the kittens, they might start to see each other in a new light. Marinette could see Adrien's soft side when he coos at the kittens. And Adrien might notice Marinette's nurturing nature. This newfound understanding can deepen their feelings for each other. They could start to be more open and honest with each other because of these shared kitten - related experiences.
In the fanfiction, the overprotectiveness might show up as the gods restricting Percy's actions. They may not let him go on certain quests alone, insisting on sending a whole entourage of helpers. This could be because they see Percy as a very important asset, and they're afraid of losing him. So they overcompensate by being overly protective.
After getting married, they would become more open and trusting with each other. Since they know each other's identities as Ladybug and Chat Noir, there would be no more secrets between them. Their relationship would be more stable and they would support each other even more in their daily lives and superhero duties.
Another reaction could be that Marinette pretends to cooperate with Adrien at first. By doing this, she can buy time and look for an opportunity to escape or get help. She might act as if she is okay with what is happening while secretly planning her next move, like leaving a clue for someone to find her or finding a way to disable Adrien temporarily.
It has a complex effect. On one hand, it can be endearing. Ron's actions might make Hermione feel special. But on the other hand, it could also make Hermione feel like Ron doesn't trust her abilities. For example, if Ron constantly hovers when she's doing magic, it might make her think he doesn't think she's a good enough witch. But as they grow and Ron learns to balance his protectiveness, their relationship can become more harmonious.
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.