Well, it's a really wild concept. In theory, it could be possible. Maybe Harry Potter, with his magic skills from his own world, could find himself in the Highschool DxD universe and for some reason decides to take Rias under his wing. He could teach her some unique magic tricks that are different from the devil magic in her world. But it would be really challenging to blend the two very different universes' magic systems and storylines in a believable way.
It's quite an interesting idea for a fanfiction. For it to work, the author would need to establish some sort of crossover mechanism. Harry could use his knowledge of the wizarding world to help Rias in her challenges in the Highschool DxD world. For example, he might help her deal with some political intrigue among the devils using his own experiences with the wizarding politics. However, it would also need to be careful not to make the story too convoluted and keep the essence of both series intact.
The idea of Harry Potter raising Rias in Highschool DxD fanfiction is fascinating. First, we have to consider the different power levels and cultures. Harry is used to the wizarding world where there are rules about magic use and secrecy. Rias is in a world of devils where power and status are very important. Harry would have to adapt to her world while also teaching her things. He could introduce her to things like the Marauder's Map which could be useful in her world for spying or getting around undetected. And his ability to think on his feet in dangerous situations could also be a valuable lesson for Rias.
Chapter 200, ", The Governor's Concept of the Phoenix", is the clearest early answer because it turns Anat's situation into a concrete plot event. It opens with Before the surgery began, Anat and his two friends were all quite... and closes on This process could take anywhere from six months to two years,.... The key payoff is that the chapter closes with "Of course, it's okay. Their condition is very stable, unlike the previous batch.
Chapter 196, ", Did I Get Exposed?", is the clearest early answer because the hidden truth stops feeling like mere subtext. The setup is On the outskirts of Weixing City, Phoenix Monastery., but the pressure keeps building through After more than half a year of construction, the Phoenix Monastery no....
Chapter 205, "The Soldier King Can Achieve It", is the clearest early answer because it turns Lacroix's situation into a concrete plot event. Early on, It must be emphasized that he was not at his full strength,.... By the end, He managed to escape, but the other two were not so lucky, nor did....
Chapter 204, ", Great Demon", is the clearest early answer because it turns Abyss's situation into a concrete plot event. A useful checkpoint is the way the scene starts with If they all died here, and the rift to the Abyss on the demon engine... and follows through with Ge Wajia malevolently aimed the bronze bell at him, and the power....
Chapter 299, ", Life is Really Tough", is the clearest early answer because it turns Subspace Inferior God's situation into a concrete plot event. The setup is Actually, Gu Hang's original plan was somewhat risky., but the pressure keeps building through Directly pulling Galaraldo's soul into the Storm God Kingdom, if....
Chapter 201, ", Maritime Relics", is the clearest early answer because it turns Gu Hang's situation into a concrete plot event. The chapter turns that into something concrete by moving from Along the way, there will be some allied supply stations, patrol... to It was as if it were indeed a relic from before the war.. What makes it stick is that the chapter closes with A Void Shield?!, which gives Gu Hang a stronger narrative position and pushes the power growth onward.
Chapter 309, ", The Governor's Speech", is the clearest early answer because it turns Alliance's situation into a concrete plot event. Early on, To all residents of Rage Owl Star:" "I am your Governor, Gu Hang.".... By the end, Seeing the owner refusing to speak, the soldier became even more.... Inside the broader family politics storyline, the chapter closes with Another chapter is coming, I'll try to have it by 3 a.m., so you all can read it tomorrow.
Chapter 329, ", Heijian Star Joins the Alliance", is the clearest early answer because a shaky connection becomes usable in the plot. A useful checkpoint is the way the scene starts with Galaraldo really left a big surprise for both Tianma Star Sector and... and follows through with The Empire approved their establishment chiefly because they were one....
Chapter 224, ", A Thought of Union Arises", is the clearest early answer because it turns Primordial Wrath Owl's situation into a concrete plot event. Early on, Although he had already formed a new Heretic Demon Hunter Squad of.... By the end, According to the last census of the Old Alliance from a few years....
Chapter 299, ", Life is Really Tough", is the clearest early answer because it turns Gu Hang's situation into a concrete plot event. A useful checkpoint is the way the scene starts with This was the core reason Galaraldo could persist for such a long time. and follows through with Wang Yuyang was extremely warm and solicitous, skirting around the....