It has the potential to be popular. The idea of Naruto being the 'king' in a High School DxD fanfiction is an interesting concept. 'Naruto' has its own rich lore and a large fan base, and 'High School DxD' also has a dedicated following. When combined, it can create a lot of interesting scenarios. For example, Naruto could bring his sense of justice and powerful ninja abilities to the somewhat chaotic world of High School DxD, which would be appealing to fans who like to see new takes on their favorite characters and universes.
Well, it depends on the fan community. Some fans might be really into this type of fanfiction because it combines the well - known 'High School DxD' universe with the allure of fairies. However, not all fans might be interested. There are those who prefer to stick to the more traditional storylines within the 'High School DxD' canon, while others are always looking for something different like this fanfiction concept.
The Highschool DxD manga is finished. It completed its journey, leaving behind a memorable story. Although it's over, its influence and popularity among manga lovers remain strong.
The Highschool DxD manga has indeed finished. It wrapped up after completing all the planned story arcs and providing a satisfying conclusion for the readers.
One interesting crossover could be the combination of Naruto's ninja skills with the supernatural elements of Highschool DxD. For example, Naruto's shadow clone jutsu could be used in the battles against the devils and fallen angels in the Highschool DxD world. And Moka from Rosario + Vampire (I assume that's what you mean by Moka) could use her vampire powers in new and creative ways when interacting with Naruto's characters. Maybe she could use her strength to compete with Naruto's taijutsu experts.
If Spawn were to interact with the main characters, he would bring a whole new level of seriousness. He has a dark past and a lot of baggage. When it comes to Issei's goal of becoming a harem king, Spawn might find it absurd but also interesting in a way. He could offer his own perspective on power and how to use it responsibly, which would be a contrast to the more carefree attitude of some of the Highschool DxD characters. And with the other characters like Akeno and Koneko, he'd be sizing them up, trying to figure out if they're threats or allies.