In a fanfiction where Naruto and Kurenai have a baby, the story could explore how the two different clans react. Naruto is from the Uzumaki clan and Kurenai is from the Yuhi clan. Their baby could be a symbol of unity between the two clans. Also, the baby might grow up having Naruto's dream of being Hokage but with Kurenai's teaching skills, which could make for a very different kind of leadership in the village.
In this fanfiction about their baby's future, the baby might face some tough decisions. With Naruto's connection to the tailed beasts and Kurenai's role in the village, the baby could be pulled in different directions. Maybe it would have to decide whether to focus on protecting the village like Kurenai or strive for something bigger like Naruto. And the baby's future relationships would also be interesting to explore, whether it would have friends from different generations due to its parents' influence.
One possible plot could be that Kurenai, seeing Naruto as a lonely and neglected baby, decides to take him in. She could then start teaching him basic ninja skills from a very young age. Naruto would grow up with a mother - like figure in Kurenai, which would change his personality in some ways. He might be more confident and less of a prankster as he has the love and support he needs early on.
One 'naruto and kurenai baby fanfiction' could be about Naruto and Kurenai finding an abandoned baby and deciding to take care of it together. They might face challenges in protecting the baby from the dangerous shinobi world.
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.
For one thing, the relationship between Kurenai and the Hokage (whichever one is in power at the time) would be put to the test. The Hokage might be initially hesitant about Kurenai's decision. But as Naruto grows under her care, it could lead to a stronger bond between Kurenai and the village leadership. Naruto's relationships with other ninja families would also be different. He might be more accepted into the social fabric of Konoha from a young age.
The baby might have some of Naruto's chakra - related powers. Since Naruto has the Nine - Tailed Fox's chakra, the baby could inherit a portion of that incredible power source. Also, Kurenai is skilled in genjutsu, so the baby could have a natural aptitude for that as well.
I'm not entirely sure if there is a specific 'Naruto cheated on by Kurenai' fanfiction. Fanfiction websites are full of a huge variety of stories, and it could be quite difficult to find one with such a specific plot. You could try searching on popular fanfiction platforms like FanFiction.net or Archive of Our Own using relevant keywords, but keep in mind that the Naruto fandom has a wide range of story themes, and this might be a rather unusual one.
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.