Well, in fanfiction, the story can be twisted in many ways. Naruto's ninja training gives him an edge in combat. He is able to analyze his opponents quickly. If in a situation where he has to kill Riser in a Highschool DxD fanfiction, he would first study Riser's fighting style. Since Naruto has experience fighting various powerful foes, he would likely find a weakness in Riser's defenses. Maybe Riser has a moment of overconfidence, and Naruto seizes this opportunity to use one of his powerful jutsu to end Riser's life.
In fanfiction, anything is possible. Naruto has his powerful jutsu like Rasengan and Shadow Clone Jutsu. If he were in the Highschool DxD universe, he might use his speed and surprise factor. Maybe he could catch Riser off - guard and land a fatal blow with a Rasengan. However, Riser also has his own set of powers in the Highschool DxD world. So it would be a very interesting and intense battle if written well in a fanfiction.
In fanfiction, such a betrayal could occur due to power struggles. Maybe Rias sees Naruto as a threat to her position in the Highschool DxD world. She might fear his growing power and influence, which could overshadow her own. So, in order to maintain her status, she betrays him.
A possible plot for a Naruto vs Riser Highschool DxD fanfiction could be that there's a power imbalance in the Highschool DxD world that Naruto is brought in to fix. Riser, who is used to being in control, doesn't like this new factor. Naruto, being the hero he is, tries to resolve things peacefully at first. But when Riser challenges him, they engage in a battle. The fanfiction could then delve into how their different power systems work together, how Naruto uses his chakra in this new magical setting, and how Riser tries to counter Naruto's unpredictable moves. It could also be about how the two grow as characters through this encounter.
In a Naruto vs Riser fight in a Highschool DxD fanfiction, Naruto would likely win. Naruto has a vast array of powerful jutsu like the Rasengan and Shadow Clone Technique. He's also incredibly resilient and has great combat experience. Riser, while strong in the Highschool DxD universe, doesn't have the same level of combat versatility as Naruto.
In a Highschool DxD fanfiction, if Naruto kills Riser, it would be a major event. First of all, the devils in the story would be in an uproar. Riser was an important figure among them. His death could lead to a power struggle among the devils to fill the void he left. Naruto would then have to face not only the devils who want revenge but also the potential chaos that his action has caused. For example, the Rating Games system might be affected as Riser was a key player in it. There could also be a shift in the relationships between different species in the Highschool DxD world, like the relationship between devils and angels might change depending on how they view Naruto's action.
A really interesting fanfiction could be where Naruto's Nine - Tails chakra has an unexpected reaction when he is near Moka. Maybe it flares up in a way that he can't control at first, and Moka's vampire instincts sense the power. This could lead to a situation where they have to work together to figure out how to control this new interaction between their powers. Also, Naruto could introduce the concept of ninja teams to the characters in Highschool DxD, which could change the way they approach battles and group activities.
Well, in such a fanfiction, Naruto might feel out of place in the Highschool DxD world. He could be heartbroken because he misses his friends from Konoha. Maybe he has a hard time adjusting to the different rules and powers in the new world.
Yes, he can. In fanfiction, the writer has the creative freedom to cross different universes. Naruto could be a father in a Highschool DxD setting perhaps through some sort of interdimensional travel or magical event. Maybe he's brought into the Highschool DxD world and starts a family there. It's all about the wild and creative ideas that fanfiction allows.
Power - up is a common theme. Fans often write about Riser getting stronger in unique ways, like mastering new magical abilities or combat techniques. It adds an exciting element to the stories.
One possible reason could be a power struggle. If Riser somehow poses a threat to Naruto's world or his friends. Naruto, being the protector, might take extreme measures. For example, if Riser was trying to take over Konoha or steal some important ninja art. Naruto would fight to defend his village and in the heat of battle, end up killing Riser.
A great fanfic idea could be that Rias and Riser are sent on a joint mission to the human world. They have to blend in as high school students. This would be a comical and interesting premise as they struggle to adapt to human life while also dealing with their own relationship. Rias might be more empathetic towards humans, while Riser could be more arrogant at first.