One plot idea could be that they meet in an alternate dimension where they are the only ones who can save that world. During their adventure, they fall in love and decide to get married. But when they return to their own world, they have to deal with the reactions of their friends and the public.
Another fanfiction concept could be a mentorship situation. Spider - Man looks up to Captain Marvel as a powerful and experienced hero. She could train him to better control his powers and also teach him how to handle the pressure of being a hero on a larger scale. This could involve some intense training sessions where Spider - Man has to push his limits, and Captain Marvel shares stories from her own experiences in the galaxy.
One idea could be that Captain Marvel and Spider - Man team up to stop a powerful alien threat that's immune to most of Earth's defenses. They'd have to combine their unique powers. Captain Marvel's energy - based attacks and flight, along with Spider - Man's agility and web - slinging skills, would make for an exciting battle.
The plot could involve a new villain who targets both of them because of their relationship. This villain might be someone who wants to disrupt the harmony between Earth and the cosmos. Spider - Man and Captain Marvel have to work together to defeat this enemy while also dealing with the challenges of their new - found married life.
One possibility in such a fanfic could be that they meet during a major inter - galactic crisis. Maybe they start off as allies, gradually realizing they have deep feelings for each other. Their different powers could combine in interesting ways to save the day, and this shared experience could be the start of their romantic journey towards marriage.
One possible fanfiction could involve Spider - Man and Captain Marvel teaming up during the Endgame battle. Maybe Spider - Man uses his agility to distract the enemy while Captain Marvel blasts them with her powerful energy. They could also have some fun banter, like Spider - Man making a joke about how Captain Marvel can fly and he has to swing around.
The plot might involve an interdimensional force that accidentally merges the worlds of Spider - Man and Captain Marvel in a way that forces them into a shared adventure. They could be in a situation where they have to protect a group of innocent people caught in this strange merge. Since they are from different hero backgrounds, they initially clash but then gradually learn to work together as they face greater threats.
A plot could revolve around Spider - Man being too cocky with his powers. Wolverine decides to train him to make him more humble and a better hero. During the training, they are targeted by an old enemy of Wolverine's. Spider - Man has to use the skills he's learning on the fly to survive. Also, there could be a sub - plot where Spider - Man struggles with Wolverine's brutal training methods but eventually realizes they are for his own good.
Another plot could be that Spider - Man is investigating a strange criminal organization and discovers Elektra has some inside knowledge. They start working together secretly. During this time, they develop feelings. However, Elektra has a dark past that threatens to come between them. But Spider - Man stands by her, and they decide to get married, vowing to face any challenges together, including those from Elektra's past.
In a fanfiction like this, there could be a lot of challenges. Their different backgrounds - Peter Parker's normal life as a student and Carol Danvers' military - turned - superhero past - could create some interesting conflicts. But they could also learn from each other. Spider - Man could teach Captain Marvel about the little joys of a normal life, and she could show him how to be more confident in the big superhero world.
One plot idea could be that Kaito decides to give up his life as a phantom thief after getting married. But an old enemy resurfaces, threatening their new - found happiness. So, they have to work together to defeat the enemy. Another idea is that they go on a honeymoon that turns into an adventure when Kaito stumbles upon a mystery related to an ancient artifact. And Aoko helps him solve it using her wits.