Perhaps an unknown hermit living in some far - off place. In many fanfics, there are mysterious characters that pop up with unique knowledge. This hermit could have mastered the Reaper Death Seal long ago and sees Naruto's potential, so decides to teach him.
Power and sacrifice are common themes. The death seal is a very powerful jutsu that often requires sacrifice, so many fanfictions explore this aspect. For example, a character might have to sacrifice their own life or something precious to use the seal effectively.
A rogue shinobi who has found a way to corrupt the Reaper Death Seal and use it for his own evil purposes. He could be stealing the souls of innocent people instead of using it as a last - resort jutsu like it was intended.
In this fanfic, Naruto might face some really tough challenges while learning the Reaper Death Seal. He could be in a situation where he has to sacrifice a lot to master it, like maybe losing some of his relationships temporarily. Also, he might have some sort of spiritual journey to fully understand the power of the seal.
One popular 'naruto reaper death seal fanfiction' is 'The Seal's Legacy'. It delves into the after - effects of the death seal on Naruto's world. Another interesting one could be 'Reaper's Redemption' which focuses on how the reaper aspect in the death seal might have a different agenda than initially thought.
Another plot idea is to have a character who is not Naruto, perhaps a new OC (original character), inherit the knowledge of the Reaper Death Seal in an unexpected way. This character could then face the moral dilemma of using such a powerful and dangerous jutsu.
One possible storyline could be that Naruto is faced with an overwhelmingly powerful enemy that he realizes can't be defeated any other way. So, in a selfless act, he decides to use the Reaper Death Seal. This would be a very tragic end for Naruto as he has so many friends and a family to live for. His death would likely send shockwaves through the Hidden Leaf Village and among his friends like Sasuke, Sakura, and Kakashi. They would be devastated, and it might also lead to a power vacuum in the village, causing all sorts of political and social unrest.
For Hinata, it would be a devastating blow. She loved Naruto deeply. She might become withdrawn and lose her usual gentle strength. Shikamaru, being Naruto's friend, would be angry at first, feeling that Naruto's sacrifice was unnecessary. But then he would realize the gravity of the situation Naruto faced. His death would also impact the younger generation. Boruto, in this fanfiction's context, would grow up without his father, and this would shape his character in a different way, perhaps making him more determined to carry on Naruto's legacy.
A 'naruto reaper of death fanfiction' likely weaves together the Naruto franchise with the idea of a reaper of death. It could be a dark and edgy take on the Naruto story. Naruto might be given the role of a reaper, either by some sort of curse or a new power bestowed upon him. This could lead to him having to make tough choices about who lives and who dies, which would be a huge departure from his normal character. His relationships with his friends and the ninja community would also be affected as they may not understand his new role or may be afraid of the power he now wields.
Since it's a Naruto - based fanfiction, Naruto himself is likely one of the main characters. There may also be other familiar characters from the Naruto series like Sasuke or Sakura, who could interact with Naruto in this new scenario involving the reaper of death.