One appropriate theme could be Naruto exploring new jutsu. For example, he could be on a journey to master a long - lost or extremely difficult jutsu, which would test his skills and determination. This would stay true to his character as a ninja constantly striving to improve.
Another great theme is exploring the backstories of minor characters. Like delving deeper into the story of Rock Lee's childhood and how his determination to become a great ninja in spite of not having natural ninja abilities was formed. It could show his early struggles and the people who inspired him along the way.
A theme centered around the exploration of different ninja techniques within the Naruto universe is also suitable. Writers could imagine new jutsus that characters discover or how they combine existing techniques in innovative ways. This can add new dimensions to the action - packed world of Naruto without delving into inappropriate content.
One appropriate theme could be Naruto's further adventures after becoming Hokage. It could explore how he manages the village, deals with new threats, and continues to uphold the values of the Leaf Village.
One appropriate theme is the growth of the characters. For example, writing about how Naruto further develops his ninja skills and becomes an even greater Hokage. This can explore his training, the challenges he faces, and how he overcomes them.
One great theme is exploring the backstories of minor characters. For example, delving into the past of Rock Lee's training and how he overcame his difficulties in becoming a great ninja.
One great theme is their relationship development after getting married. It could focus on how they build a family together, raise their children, and face the challenges of being a shinobi couple. Another theme could be their adventures as a team, perhaps going on a special mission together that tests their bond and skills.
Appropriate themes in Naruto fanfiction include character development. For example, exploring how Naruto further develops his Sage Mode or how Sasuke comes to terms with his past and finds his place in the village. Another theme is the exploration of new jutsu. Writers often create new techniques for the characters to use in battles.
The idea of 'birth fetish' in fanfiction is inappropriate and often goes against ethical and moral standards. Some great alternative Naruto - related fanfiction themes could be exploring different character backstories, like how Kakashi became so skilled at a young age. Another could be focusing on the relationships between the characters in non - inappropriate ways, such as the friendship between Naruto and Shikamaru. And there could also be fanfictions about new adventures that the Naruto characters could go on, like exploring a new and mysterious land outside of the Hidden Villages.
A possible theme is about teamwork. Maybe these characters are part of a group that has to work together to defeat a common enemy. Their physical appearance, including the 'big breasts' if it's part of their design, is just a small aspect, and the main focus is on how they use their ninja skills and cooperate with each other to succeed in their tasks.
You could write a Naruto fanfiction about a time - travel scenario. For example, Naruto gets sent back in time to the era of the First Hokage. He has to adapt to the different ways of that time while also trying to prevent a great disaster that he knows is going to happen in the future. Another idea is to focus on the relationship between Naruto and his mother, Kushina. How would their relationship develop if she were still alive? And a third option could be a fanfiction where Naruto and his team have to solve a mystery within the Hidden Leaf Village that has been hidden for generations.