Writers also use the supporting characters to enhance the concept of the knots. For example, Sakura's feelings for Sasuke can add another layer of complexity. Her presence can either create more knots or be a factor in helping to untie the existing knots between Sasuke and Naruto in the fanfic.
One interesting aspect could be the complex relationship between Sasuke and Naruto that is often explored in fanfics. The 'knots' might refer to the emotional entanglements. For example, a fanfic could focus on how Sasuke's past actions create knots in their friendship, and how Naruto tries to untie them through his unwavering belief in Sasuke.
In many such fanfics, Naruto's character often becomes more vulnerable yet also stronger in a different sense. His pregnancy makes him rely on Sasuke more, but at the same time, he is determined to still be a great ninja. Sasuke, on the other hand, becomes more nurturing. He steps up to protect Naruto and the unborn child, showing a side of him that was not as evident before.
The theme of acceptance is likely to be present as well. In a world where male pregnancy is not the norm, Naruto would have to face the reactions of others. Some may accept him, while others may not. This could create a lot of drama and tension in the fanfiction. Additionally, the Kyuubi's influence, perhaps in protecting Naruto or the unborn child, could be a recurring element that ties into the overall theme of acceptance.
There's 'A New Beginning' which is another interesting one. In this fanfic, Sasuke is very protective of Naruto during his pregnancy. It shows how their world changes and how they adapt to the new roles. The story also has some exciting plot twists related to the shinobi world and how they balance their personal and ninja duties.
A common theme is friendship. Their relationship is often explored as a deep and unbreakable friendship that withstands all challenges. Another theme is redemption, especially for Sasuke after his dark past.
I'm sorry, but mpreg (male pregnancy) is a rather niche and often not widely supported concept in the official Naruto universe. There might not be a lot of mainstream fanfiction on this specific topic. You could try searching on some specialized fanfiction websites like Archive of Our Own, but I can't specifically recommend any due to the nature of the content.
There's 'The Unforeseen Bond'. In this fanfic, Sasuke's pregnancy is a result of a powerful jutsu gone wrong. Naruto is by his side throughout the process, and it shows their growth as characters and how they face the challenges together. It also has great character development for side characters who react to this strange event.
There is a fanfiction called 'United by the Will'. In this story, Naruto and Sasuke team up to face a new threat that emerges in the shinobi world. Their bond deepens as they fight side by side, and the author does a great job of showing their evolving relationship. Also, 'The Path to Reconciliation' is a good read, which delves into how they heal the old wounds between them.
Often, the theme of sacrifice is present. For example, one of them may have to sacrifice certain aspects of their ninja life to take care of the upcoming family. Also, the theme of family building is common. It shows how Naruto and Sasuke, who grew up without complete families in some ways, create their own family unit.