One possible plot could be that Issei's injury was the result of a new and powerful enemy. This enemy could be targeting Issei specifically because of his growing power and influence in the supernatural world. His friends would then have to rally around him to help him recover and also find a way to defeat this new threat.
Maybe the injury was an accident during a training session. Issei could be overexerting himself in an attempt to master a new power or technique. This would lead to his friends, especially the more experienced ones like Sirzechs or Azazel, having to step in and guide his recovery, while also teaching him the importance of proper training and pacing.
One possible plot could be how the Occult Research Club copes with Issei's death. They might struggle to move forward while also trying to figure out who was behind his death. Maybe they suspect a powerful enemy from the Underworld or a rogue devil. Another idea could be that Issei's death sets off a chain of events that leads to a new power struggle in the supernatural world, as different factions vie for the power he once held or the influence he had over certain areas. And his friends could be visited by his spirit in dreams, guiding them to uncover secrets he didn't have time to reveal before his death.
One idea for a fanfiction about Issei's birthday could be that the Occult Research Club throws him a surprise party. They decorate the clubroom with all his favorite things, like pictures of his favorite heroes and a big banner that says 'Happy Birthday Issei'. Rias could present him with a special gift, perhaps a new piece of sacred gear that has been customized just for him.
One interesting plot could be Akeno and Issei going on a secret mission together. They face various challenges and their relationship deepens during the process.
One interesting plot is when Issei's peerage has to face an unknown and powerful enemy from a different dimension. This forces them to develop new powers and strategies. Another plot could be about Issei's peerage members having to deal with a curse that affects their relationships and powers within the group.
In a fanfiction, it could be that Koneko and Issei are chosen for a special mission by the Gremory group. They are initially hesitant to work together as they have different approaches. However, as the mission progresses, they start to complement each other's styles. Koneko's stealth and Issei's more upfront fighting style work in harmony to defeat the enemy and complete the mission, and in the process, their relationship grows.
One great fanfiction idea could be that Issei discovers a new power within himself that is directly linked to Rias's heritage. Maybe he can tap into an ancient magic that only works in harmony with Rias's own powers. As they train together to master this new ability, their relationship deepens beyond just the typical master - servant bond in the Highschool DxD world.
One great fanfiction idea could be Issei and Irina going on a special adventure together in the world of Highschool DxD. Maybe they discover a hidden power or a new realm. They could face challenges that test their relationship and grow stronger as a result.
In a fanfiction, Issei and Koneko could be paired for a school project. At first, they struggle to work together because of their different personalities. Issei is more outgoing and impulsive, while Koneko is quiet and reserved. But as they dig deeper into the project, they start to understand each other better and develop feelings for one another.
A fanfiction idea could be that Issei and Xenovia get transported to a different dimension. In this new world, they are separated from their friends and have to find a way back. Issei tries to keep Xenovia's spirits up as they encounter various strange creatures. They discover new powers within themselves during their journey. Xenovia might also learn more about Issei's pervy side and they have some comical moments while still trying to figure out how to return home.
Well, given that 'High School DxD' is a popular anime, this fanfiction might be about Issei's character development in a new or different way. Maybe it delves deeper into his relationships with other characters in the series. However, the 'orgasms' part in the title is a bit unclear. It could potentially be some sort of over - the - top or comical take on his emotions or reactions within the story's context.