The main problem is that it completely distorts the original characters. Naruto has his own set of relationships, goals, and a world that revolves around ninja and his friends in Konoha. Koneko has her own story in the High School DxD world with different rules about magic and the supernatural. Combining them in this way for this kind of plot is disrespectful to the original creators' intentions and the essence of the characters.
There might not be any 'appropriate' fanfiction of this nature. Naruto and Koneko are from distinct anime worlds, and creating a plot where Naruto gets Koneko pregnant is not only a strange combination but also might violate the integrity of the original characters and their respective storylines. In the world of fanfiction, there are many other positive and creative ideas to explore rather than this rather inappropriate one.
It depends on different perspectives. From a purist point of view, it's likely to be seen as inappropriate because it may distort the original intention of the source material. But for those who view fanfiction as a space for unrestricted creativity, it could be seen as an interesting exploration. However, it should be noted that if the work is shared publicly, it may receive a lot of criticism due to the sensitive nature of the topic.
There could be consequences within the story itself as well. It might change the entire future arc of both Issei and Koneko in ways that are difficult to reconcile with the original character traits. For example, their relationship dynamics would be completely altered, and they would have to deal with the responsibilities of pregnancy, which could be a very different direction from what the original work intended. Additionally, other characters in the fanfiction might also be affected by this new development and their reactions could be hard to predict and write in a believable way.
The main problem is that it's completely against the canon. Dumbledore is a much older and mentor - like figure to Harry, and the idea of such a relationship is inappropriate and goes against the moral and ethical framework of the original story.
One major problem is that it goes against the nature of the relationship between Sirius and Harry in the original 'Harry Potter' series. Their relationship is more of a mentor - mentee or a father - son like bond, not a romantic or sexual one.
One problem could be that it might change the perception of the original characters in an unwanted way. Fans who love the original relationship between Ash and Lillie might not like this new, more adult - themed take.
One major problem is that it goes against the moral values of the Naruto series. Naruto is about equality and respect among characters. A slave concept is the opposite of that.
One problem is that it goes against the characters' established personalities. Hinata is a strong - willed character with her own values and Naruto respects others. Another issue is that it's a very unethical concept. Slavery has no place in the Naruto world which is about friendship and growth.
One problem is that they are from different fictional universes. Naruto's world has its own set of rules, characters, and themes related to ninja life, while Bastila is part of the Star Wars universe with its own complex lore about the Force and galactic politics. Combining them in a sexual way is a very forced and inappropriate mash - up.
One challenge could be the difference in their powers. Naruto has his ninja powers while Koneko has her own unique abilities. They might have trouble coordinating in battles at first.