Well, perhaps in the fanfiction, Naruto being Kurenai's sensei could lead to him teaching her some unorthodox methods. Since Naruto has his own way of doing things, he might introduce her to new ways of fighting or thinking that completely revolutionize her ninja skills. This could create interesting storylines where Kurenai has to adapt to Naruto's teaching style while still holding on to her own values.
Their relationship could start off rocky as Kurenai might be hesitant to accept Naruto as her sensei. After all, Naruto is younger and has a very different style. But as time goes on, she would start to see the value in his teachings.
Tenten could be one of the characters. She could be Naruto's friend and also have a bit of a crush on him. Ino might also be present, using her mind - related jutsu to try and understand the complex relationships in the harem. Rock Lee could show up too, providing some comical relief and also being Naruto's loyal friend in the midst of all the relationship chaos.
In the fanfiction, Naruto's new sensei could be a mysterious figure who has ties to the Sage of Six Paths. This person might have been waiting for the right time to appear and train Naruto. They could possess knowledge about the origin of chakra and how to fully unlock Naruto's power. It could also be someone who was once an enemy but has now changed their ways and wants to use their skills to train Naruto for the greater good of the ninja world.
There's a chance that Naruto's new sensei could be a self - taught ninja who has developed their own unorthodox style. This person sees Naruto's ability to think outside the box and wants to refine that in him. They could introduce Naruto to a new way of looking at chakra control and combat strategies that are completely different from what he has been taught so far.
I think Orochimaru would be the most unexpected sensei. Usually, he's seen as a villain, but in a fanfiction, if he were to train Naruto, it would be extremely unexpected. He has a vast knowledge of jutsu, especially forbidden ones. He could teach Naruto some very powerful and unique abilities, but at the same time, Naruto would have to deal with Orochimaru's morally ambiguous nature.
One aspect to consider in this fanfiction scenario is how their marriage would affect the other characters. The young ninja in the village might look up to them as a couple. Naruto's friends like Sakura and Sasuke would have different reactions. Sakura might be happy for Naruto but also a bit envious, while Sasuke might initially be skeptical but come to respect their relationship over time. And their family life could involve Naruto teaching their future children his unique ninja skills, while Kurenai imparts her wisdom about the more subtle aspects of being a ninja.
I'm not entirely sure if there is a specific 'naruto is kurenai son fanfiction' out there. Fanfiction platforms are filled with all sorts of creative ideas, but it can be difficult to know for sure if there is one specifically for this concept. You could try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own. Maybe start with searching for Naruto - Kurenai family relationship or something similar to see if any relevant stories pop up.
In most Naruto fanfictions, there is no such plot where Kurenai cheats on Naruto because they don't have that kind of relationship in the original story. Kurenai has her own story arc mainly related to Asuma. So it's very unlikely to find such a scenario in regular Naruto fanfictions.
Tenten would also be an interesting choice. She could focus on weapon - based combat training for Team 7. Since she has extensive knowledge of all kinds of weapons, she could introduce new and unique weapon techniques to the team.