At first, he's likely to be shocked. Issei is often portrayed as a character who trusts easily, so betrayal would come as a big surprise. He might not believe it at first and try to find reasons to justify the actions of the person who betrayed him.
Often, a power - hungry character might betray Issei. In the world of the fanfiction, power is crucial. So, someone who wants more power than Issei may see him as an obstacle. They could betray him by stealing his power - up opportunities or even directly stealing his power if there's some sort of magic or ability transfer in the story. Also, a character with a hidden agenda related to the overarching plot of the fanfiction world, like a secret organization trying to control the balance of power between devils, angels and fallen angels, could use Issei and then betray him when he has served their purpose.
I'm not entirely sure as the description is rather unclear. It could potentially be about a character named Issei in the 'DxD' universe and some sort of action related to a fanfiction about him. Maybe it's about exploring or creating a fan - made story where Issei is involved in a stroking action, though without more context it's hard to be specific.
Issei could develop by learning the discipline and self - control that comes with being an exorcist. This would contrast with his more impulsive devil - side nature. For example, he might have to resist the urge to use brute force and instead use the more strategic and spiritual techniques of an exorcist.
Issei develops by facing various challenges. Each encounter in the harem and with the milf - hunting situations makes him grow. He becomes more confident over time.
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.
Naruto's transformation abilities like Nine - Tails Chakra Mode would also be very impactful. The increased power and the unique appearance of this mode would intimidate his enemies. In the world of DxD, where appearances and auras play a role in battles, this could be a great advantage. He could also use the chakra of the Nine - Tails to heal himself, which is something that could come in handy during long and tough battles in Issei's world.
I'm afraid it's not easy to give a clear - cut meaning. 'DxD' might be short for 'High School DxD', a series with various characters like Issei. But'stroking' in relation to 'fanfiction' is an odd combination. It could potentially mean that Issei, within the realm of fan - created stories, is having some form of interaction that is being described as'stroking', perhaps like caressing or nurturing the ideas in the fanfiction, but this is just a wild guess.
One big part of the appeal is the potential for epic battles. An Evil Dragon Issei would be extremely powerful, so there could be intense fight scenes against other powerful foes. Also, it gives writers a chance to delve into the more complex aspects of his personality. Maybe he has to struggle with new emotions and desires that come with the Evil Dragon form. And it can add a layer of mystery as readers try to figure out how he got to this point and if he can ever go back.