why does pain have rinnegan

It could be that he exercised too vigorously and pulled a muscle in his stomach area. Or perhaps he has some kind of digestive problem like indigestion or an ulcer.

In fanfiction, absolutely. Fanfic writers often like to play with the concepts and powers in the Naruto world. Giving Naruto the true Rinnegan can open up a whole new realm of possibilities for the story. It can change the dynamics of his relationships with other characters, as they might react differently to his newfound power. Also, it can lead to the exploration of different plotlines, such as Naruto having to master the Rinnegan's unique abilities, which could be very different from his already known Sage Mode and Nine - Tails powers.

Maybe she is a very empathetic person. Pain stories can be quite distressing, and she might not want to expose herself to that kind of negative emotion.

It could be that in this fanfiction, Naruto inherits the Rinnegan from a long-lost ancestor, unlocking hidden powers and facing new challenges.

Well, the Naruto vs Pain fight in the original series is epic. Fanfiction allows fans to explore different scenarios and what - ifs. Maybe they want to see different character developments during that intense battle.

Yes, Naruto acquires the Rinnegan in the manga.

Yes, Naruto does obtain the Rinnegan in the manga.

The Rinnegan is often neglected in Naruto fanfiction perhaps because it represents a very high level of power that can be intimidating for writers to handle. If a writer wants to create a more relatable or character - driven story, they might shy away from using the Rinnegan. Additionally, the fanfiction community may have certain trends that favor other elements of the Naruto universe over the Rinnegan, so it doesn't get as much attention.

Whether the ending of a novel was good or bad, it would cause a faint pain in the heart. This was because the ending of a novel usually had a profound impact on the development of the plot and the fate of the characters. The readers would often have emotional resonance and emotional conflict. When the ending of the novel is good, the readers will feel satisfied and happy, and at the same time, they will be pleased with the development of the story and feel hope and comfort for the fate of the characters. This kind of emotional recognition and hope would make the readers feel psychologically satisfied and at peace. When the ending of the novel is bad, the readers will feel disappointed and depressed, and at the same time, they will feel confused and uneasy about the development of the story. This kind of emotional frustration would make the reader feel psychological pain and uneasiness. Therefore, the ending of the novel was very important to the readers. A good ending could allow the readers to better understand the story, create a better reading experience, and also allow the readers to better feel the emotional resonance and sense of hope.

Another possibility is that it's a result of some strange chakra experiment gone wrong (or right). Scientists in the Naruto universe are always dabbling in chakra research. Maybe an experiment meant to enhance her natural abilities instead gives her the Rinnegan, and she then has to learn to control it quickly to avoid being consumed by its power.