Well, in fanfic, anything can happen. Naruto is known for his creativity and adaptability. Maybe he discovers a new chakra - based metal - forging technique. He could combine his Rasengan's spinning energy with some sort of metal - shaping jutsu to mold the sword.
In fanfic, Naruto might make a sword as a result of a unique mission. He could be in a place where he needs a weapon other than his regular ones. So, he uses his knowledge of ninja tools and his own chakra to create a sword. For example, if he's in a dimension where normal kunai and shuriken don't work, he might make a sword that can cut through the strange barriers there.
One possibility is that Naruto makes a sword to honor someone. He could have learned about an ancient sword - making art from a scroll or an old ninja. Inspired by their story, he decides to make a sword. He puts his own spin on it by infusing it with his own chakra signature, making it a one - of - a - kind weapon that represents his growth and his connection to the ninja way.
Well, in the Naruto universe, for Naruto to make a Treant Jutsu, he might first need to study nature chakra deeply. He could observe how trees grow and thrive, and then try to infuse his own chakra with the essence of nature. Maybe he'd have to combine his shadow clone jutsu in a new way, having clones study different aspects of trees, like their root systems and how they absorb nutrients. Then he could use his Rasengan as a base and add the nature - based tree - like elements to it, gradually forming a Treant - like structure out of his chakra.
Well, in fanfiction, Naruto might make a sword that has his own personal touch. It could be made from a rare material he discovers on one of his adventures. He would probably engrave it with symbols that are meaningful to him, like the Uzumaki clan symbol. And it could be a sword that can change its form depending on the situation, like from a short sword to a long katana.
He could find it during one of his missions. Maybe he's exploring an ancient ruin and stumbles upon the sword. It could be in a hidden chamber protected by some traps that Naruto has to overcome using his skills and wits.
It's just a wild concept in yaoi fanfic. Maybe the author wants to explore the extreme of relationship dynamics and gender - bending ideas. Since it's fan - made, there are no real - world rules to limit it. They can create a whole new set of rules within their fictional story to make Naruto pregnant, like introducing some super - rare jutsu that can change a male's biological function.
The story in this fanfic might center around Naruto's motivation for creating the seantent sword. Perhaps he wants to create a weapon that can defeat a new and powerful enemy. He might have to travel to different places in the Naruto universe to find the right components for the sword. And during this process, he could learn more about his own powers and the history of his world.
It could have the power to cut through almost anything. Since Naruto is a powerful ninja, the sword might inherit some of his chakra's strength, allowing it to slice through thick barriers or even powerful jutsu defenses.
Perhaps Naruto has a newfound confidence or a change in his personality that makes Kiba and Issei twitchy. In the fanfic, if Naruto starts acting more recklessly or assertively than usual, it might make them nervous. It could also be that Naruto has some sort of connection to an enemy or a dark force that Kiba and Issei sense, and that's what is making them twitchy.
In a Naruto becomes immortal fanfic, it could be possible through some unique jutsu. Maybe he discovers a long - lost forbidden jutsu that halts the aging process. For example, he might find a scroll in an ancient ruin that contains the knowledge of immortality. Another way could be through some sort of pact with a powerful and immortal being. This being could grant Naruto immortality in exchange for a great service or sacrifice.
One way this could work in the fanfic is through a time - space distortion. Imagine that a rip in the fabric of reality opened up between the world of Naruto and the realm of the Greek gods. Zeus and Hera, being curious or having some grand plan, sent a part of their essence through this rift. This essence then combined with elements in the Naruto world, resulting in Naruto being born as their son. This would also bring about all kinds of new powers and abilities for Naruto, as he would inherit some of the divine qualities of Zeus and Hera.
It could be a comical take in the fanfic as well. Maybe a crazy inventor or a bumbling wizard accidentally casts a spell that merges the two worlds in a strange way, making Sephiroth Naruto's brother. This would lead to hilarious situations like Sephiroth trying to understand Naruto's love for ramen or Naruto being baffled by Sephiroth's long, flowing hair and his rather dark and brooding personality.