In some fanfictions, Issei's character develops by becoming more mature. He realizes the consequences of his actions more deeply. For example, when he uses his powers, he starts to consider the collateral damage and tries to minimize it, which is a big step from his more impulsive self in the original story.
In many fanfictions, Issei's character develops in terms of power. He starts as a relatively weak character and gradually becomes stronger through training and various challenges. For example, he might learn new techniques from a mysterious mentor or gain new powers from a magical artifact.
Issei could become more mature. He might be less impulsive and more strategic in his actions. For example, in battles, instead of just charging in, he would plan his attacks better.
Issei's character development in Highschool DxD fanfiction can be quite diverse. In many fanfictions, he may become more powerful at a faster rate than in the original series. This could be due to different plot devices or new mentors introduced in the fan - created stories.
It could start with them being forced to work together on a mission. At first, they might clash due to their different personalities. Issei is more impulsive and Yubelluna is more reserved. But as they face difficulties during the mission, they start to understand each other better. For instance, when Issei rushes into a fight without a proper plan, Yubelluna scolds him but also helps him out. This back - and - forth gradually turns into a more affectionate relationship.
In relationships with potential love interests, his coldness can be a major obstacle. If he was previously a warm and friendly person towards a girl he liked, the sudden coldness could make her think he's no longer interested. This can create a lot of misunderstandings and drama in the fanfiction.
In fanfiction, Issei might also develop morally. He could be faced with tough decisions where the line between right and wrong is blurred. This forces him to think about his actions more carefully and develop a stronger sense of justice, rather than just acting on impulse like he sometimes does in the original story.
Issei's character often develops by becoming more powerful. His Boosted Gear evolves, and he learns to control it better. For example, he might gain new abilities or forms in fanfiction.
Yes, there might be. There are a vast number of fanfictions out there for various combinations of popular culture elements. Since Highschool DxD has a large fan base and Godzilla is an iconic figure, it's not unlikely that some creative fans have combined the two in a fanfiction. You can try searching on popular fanfiction websites to find such works.
There could be. Fanfiction writers are known for their wild and creative crossovers. Given the popularity of Highschool DxD and the unique concept of Guyver, it's entirely possible that an Issei - Guyver fanfiction exists. You might want to check popular fanfiction websites like Archive of Our Own or FanFiction.net. Just search for relevant keywords like 'Highschool DxD Issei Guyver' and see if any relevant stories pop up.
There are fanfictions where Issei leaves to protect others. He might learn of a great danger that is coming and decides that the best way to keep his friends and loved ones safe is to remove himself from the situation. So, he leaves, hoping that the enemy will follow him instead of targeting those he cares about.