One common theme is the struggle of single parenting. Naruto has to handle all the responsibilities of raising a child alone, like providing for them, protecting them, and teaching them right from wrong. Another theme is the clash of different worlds. Since it's a crossover, there are elements from different anime universes that Naruto has to deal with while raising his child.
There's also 'Naruto: Single Father in a Fantasy Crossover'. This story focuses on Naruto raising his child in a world full of magic and different races from other animes. He struggles to fit in at first but then uses his determination and the values he learned in the Naruto world to build a good life for his family. It has a great plot that keeps you hooked.
One common theme is the struggle of balancing ninja duties and fatherhood. Naruto has to be out there protecting the village but also be there for his child.
One possible storyline could be Naruto struggling to balance his ninja duties with raising his child alone. Maybe he has to take the kid on missions sometimes, teaching the little one about the ninja world along the way. Another could be Naruto dealing with the judgment of the village as a single father, showing how he overcomes that and still raises a strong and kind - hearted child.
There might be a fanfiction where Naruto becomes a single father because of some unforeseen circumstances during a mission. He then has to teach his child the ways of the ninja world while dealing with his own emotional turmoil. This could explore how Naruto's past experiences shape his parenting style.
In single father fanfiction, Naruto's character often develops a new level of patience. He has to deal with his child's tantrums and needs, which is different from his ninja battles. This makes him more empathetic.
Another theme is growth. Naruto grows as a person and as a father. He learns new things about himself and about parenting. He might start out not knowing how to make a proper meal for his child but by the end of the fic, he's a master chef for his little one. There's also the theme of protection. Naruto will do anything to protect his child from harm, whether it's from other ninjas or just normal everyday dangers in the village.
He would become more empathetic. As a single father, Naruto would have to understand his child's feelings more deeply. He'd be quicker to pick up on when the child is sad or happy, and adjust his parenting accordingly. For example, if his child is sad about not having a mother, Naruto would have to be extra sensitive.
One popular 'naruto is a single father fanfiction' might be 'Naruto's New Beginning'. In it, Naruto faces the challenges of raising his child alone while still being a hero in the village. Another could be 'Single Father Naruto: The Struggles and Triumphs' which delves deep into how he manages his ninja duties and fatherhood.
In some 'naruto is a father crossover fanfiction', there could be a storyline where Naruto is a father in a crossover with the Harry Potter world. His child could be a student at Hogwarts, and Naruto, with his experience of being a hero, tries to understand the magic world and protect his child from the dark forces. Maybe he uses his chakra in unique ways within the magical environment.