A great plot idea could be a competition - based story. There's a big tournament in the school where different teams compete. Asia and Gasper form a team, even though they seem like an unlikely pair. Along the way, they face stronger opponents, but they learn to combine their skills. Asia can heal their injuries during the battles, and Gasper can use his power to surprise the enemies at crucial moments. They also grow closer as friends during this tournament, facing not only external enemies but also internal doubts about their abilities.
One plot idea could be Asia and Gasper teaming up to solve a mystery within the school. Maybe there are strange disappearances and they use their unique abilities to figure out what's going on. Another idea is a story where they go on a journey to find a magical artifact that can help protect their friends. And a third could be a slice - of - life story where they help each other deal with personal problems like Gasper's shyness and Asia's insecurities about her new life in the supernatural world.
A really interesting plot could be Gasper getting transported to a different dimension or a parallel world within the DxD universe. In this new place, he has to rely on his wits and the basic powers he already has to survive and find a way back home. Along the way, he meets different versions of the characters he knows, and through his interactions, he learns more about himself and his place in the grand scheme of the DxD world.
For Asia, her character could be developed by exploring her past more deeply. Maybe she could have flashbacks to her life before joining the supernatural world, which would help explain her kindness and her eagerness to help others. As for Gasper, he could be made to overcome his extreme shyness. For example, by being put in situations where he has to speak up to protect Asia or their friends. This would show his growth and development.
One idea could be a new student arriving at the school who has a unique power that catches the attention of the main characters. For example, a girl from a far - off land who can manipulate time in small ways. This could lead to adventures where they have to fix time - related mishaps in the school. Another plot could involve a love triangle between a human student, a devil, and an angel, all trying to navigate their feelings while also dealing with the politics of the three factions in the Highschool DxD universe. Maybe there could be a school event like a tournament where the characters team up in unexpected combinations to compete, and during this time, romantic feelings start to develop.
One idea could be Gasper using his unique powers to protect his harem members from a new threat in the high school. Maybe a group of rogue devils tries to target the girls he cares about.
Fanfiction could also develop Gasper by exploring his relationships in more detail. His friendships, his crushes, or his mentorships. For example, if he has a mentor figure who teaches him how to better control his powers, we can see how that relationship evolves over time and how it impacts Gasper's growth as a character. We can also see how his friendships are tested in tough situations, and how he responds, which would show his loyalty and the values he holds dear.
The unique personalities of Gasper and Xen. Gasper is a rather complex character, and Xen brings something new to their dynamic. Their relationship has the potential for a lot of growth and interesting interactions.
For a fanfiction with Issei and Asia married, a great plot could be that Asia discovers a new power within herself after getting married. This power could be related to their combined love and it attracts the attention of an ancient and evil force. Issei then has to train Asia to control this power while also protecting her from the approaching danger. Or perhaps they are chosen to represent their respective groups in a tournament that has high stakes for the future of their relationship and the groups they belong to.
When exploring fanfics, keep in mind the quality of writing. Look for ones with good grammar and engaging storylines. Some fanfics might focus on a particular aspect of their relationship, like how they support each other during difficult times in the Highschool DxD world, while others could be more light - hearted and focus on their daily interactions.
One great fanfic could be 'Issei and Gasper's Unlikely Bond'. It delves into how their friendship develops in a unique way, with some exciting adventures in the Highschool DxD universe. They face challenges together and support each other, which is really heart - warming.
One interesting plot idea could be Murayama getting involved in a magical mystery within the Highschool DxD universe. Maybe she discovers a hidden power and has to learn to control it while dealing with the normal high school drama and the supernatural elements around her.