Power and responsibility are common themes. Since Issei is the son of Sparda, he often has great power, and he has to learn how to use it responsibly. Another theme is identity. He has to figure out who he is in relation to his father and his own place in the world. Family legacy also plays a big role as he is constantly living up to or trying to break free from the expectations of being the son of Sparda.
There's a fanfiction where Issei's son has a unique power that sets him apart. In this story, he has to learn to control it while also handling the typical Highschool DxD drama like rivalries and romances. The author does a great job of showing how he struggles with being in his father's shadow at times, but also rises above it in his own way.
One prevalent theme is likely to be the battle between good and evil. Given the nature of the characters, Issei as the son of Azazel may be caught in the middle of this eternal struggle. He may have to decide which side to take or find a way to balance the two. There could also be themes related to family secrets and the revelations that come with uncovering them, which add to the drama and intrigue in the fanfiction.
Romance is also a big theme. Just like in the original Highschool DxD, his son usually has his own love interests. These relationships can be complicated by his status as Issei's son. Sometimes, potential partners are attracted to him because of his family name, and he has to figure out if their feelings are genuine.
I'm not sure of specific 'issei son of azazel fanfiction' off - hand. But you can try searching on fanfiction - dedicated websites like Archive of Our Own. There might be various stories there that explore this concept.
One of the things that makes Issei Son of Lilith fan fiction appealing is the potential for world - building. The writer can create a whole new world around this concept. They can introduce new characters related to Lilith's side of the family or new realms that are connected to Issei's new heritage. It can be a rich tapestry of new ideas and concepts that draw readers in and make them want to explore this alternate version of Issei's story.
Well, one popular 'issei son of sparda fanfiction' might be 'The Ascent of Issei Son of Sparda'. It focuses on Issei's journey as he discovers his heritage as the son of Sparda and his battles against various demons. Another one could be 'Issei's New Path' which shows his growth in power and character development in an interesting way. There's also 'Issei Son of Sparda: The Hidden Powers' which delves into the unique powers that Issei might inherit from his father.
One interesting plot could be Issei exploring his new divine heritage. Since Amaterasu is a powerful goddess in Japanese mythology, he might discover new powers related to the sun. For example, he could have the ability to emit intense heat or blinding light, which would be a great addition to his combat skills in the Highschool DxD universe. Another plot could involve the reactions of his friends and enemies to this new revelation. His friends might be in awe or a bit jealous, while his enemies could see him as an even greater threat.