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.
One common theme is power struggle. Since Percy has two very different sources of power as a demigod and as the Son of Sparda, he often has to figure out how to control and use them. Another theme is identity. He has to reconcile his two identities and figure out who he really is.
Often, themes of family and identity might be common. Since it's about a son, exploring his relationship with his father Michael could be a big part.
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.
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 common theme is the clash of two different worlds. Naruto's world of ninjas and Angelo Sparda's more demon - related world can create a lot of interesting scenarios. Another is the idea of power and how they each use their unique powers in different ways.
In 'Vergil Sparda crossover fanfiction', a frequent theme is the exploration of new powers. As he enters different universes, he may encounter new forms of magic or technology that he can either incorporate or fight against. Another common theme is friendship or enmity. He forms new relationships, whether it's a friendship with an unlikely character or an intense rivalry. And there's always the overarching theme of how his actions in the crossover affect his own world and the new one he's in, which can lead to some really complex and interesting storylines.
Another theme is the idea of hidden lineages or connections. Many fanfictions play with the idea that there is some long - lost connection between the Potter family and Lord Sparda's world. This could be through an ancient prophecy or a secret pact made generations ago. It adds an element of mystery and discovery as characters try to figure out these connections.
Many fanfictions focus on Issei's role within the devil society. How he rises in rank, earns respect, and changes the way things are done. There are also themes related to loyalty and friendship. His relationships with his friends and comrades are often explored, showing how they support each other in the face of various challenges in the dangerous world of 'High School DxD'.
Well, the theme of sacrifice is quite prevalent. Sometimes either Issei or Rias has to sacrifice something for the other or for the greater good. Another common theme is identity. Issei, as a human - turned - supernatural being, and Rias, as a devil, both struggle with their identities at times. Their relationship helps them to better understand themselves. And the theme of destiny often comes up, as if they are fated to be together and face all these challenges as a couple.