Marinette could react with disbelief and assume it's some sort of joke at first. But when she realizes Adrien is serious, she might start to get really nervous. She could start fidgeting with her hands or her hair. If she's in the middle of doing something, like working on a design, she might drop her tools in surprise. Once the shock wears off, she would most likely be very happy and accept his invitation, but it would be a very flustered and excited acceptance.
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.
One possible scenario could be that Adrien finally gathers the courage during a school event. Maybe it's at a dance where they are sharing a slow dance and he just blurts it out. Another could be that he plans a really elaborate date first, like a picnic in a beautiful park that he knows Marinette loves, and asks her out there. Or perhaps he asks her out after she has helped him with something really important to him, like when she designed a special piece for his father's fashion line and he realizes how amazing she is and that he wants to be more than just friends.
Marinette might be initially shocked when Adrien steps in to protect her. She could be very grateful and show it with a shy smile or a simple 'Thank you.'
He could also be a bit worried. Adrien might think about the responsibilities that come with having a child. He might wonder if they are ready for this big step, considering their own lives and any potential challenges. He would then sit down with Marinette and have a serious conversation about how they are going to handle everything.
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.
One idea could be that Adrien initially feels shocked but also a sense of relief. He might have always had a feeling that Marinette was special, and now it all makes sense. So he starts to view her in a whole new light, with more respect and admiration for her dual identity.
Marinette would likely be very frightened at first. She might scream or try to fight back. After all, being kidnapped is a terrifying situation.
Alya would probably be super excited and start planning everything from baby showers to future playdates. She'd be there for Marinette every step of the way, giving advice and support. Nino might be a bit more reserved at first but would soon warm up to the idea and be a great source of comfort for Adrien, like helping him pick out baby clothes or build nursery furniture.
Once upon a time, Marinette and Adrien's big day finally arrived. The city of Paris was adorned with flowers and ribbons. Marinette, in her beautiful white gown, walked down the aisle. Adrien, looking dashing in his suit, had tears of joy in his eyes. Their friends and family watched with love. As they said their vows, the whole place was filled with an air of magic. And then they were pronounced husband and wife, sharing a passionate kiss as confetti rained down on them.
A great element in such a fanfiction could be the family aspect. Maybe they start thinking about having children. How would they raise their kids? Would their children inherit their superhero powers? And how would they protect their family from the villains in their world? Their friends like Alya and Nino could also play important roles in their married life, perhaps as godparents or just as good friends who are always there to offer advice and support.