One possible plot could be that Naruto somehow travels back in time and meets Rin. He might try to prevent her tragic death. Since Naruto is known for his determination and never - give - up attitude, he could use his skills and knowledge to change the events that lead to her death.
Naruto would probably be very surprised. He has heard about Rin from Obito and Kakashi. So when he actually meets her, he might be at a loss for words at first.
Their relationship could start off as a bit rocky. Inuyasha might be a bit impatient with Rin's naivete at first. But as they face challenges together, like fighting off demons or finding their way through a maze - like forest, they start to respect each other. Rin would look up to Inuyasha's strength, and Inuyasha would come to appreciate Rin's kind heart.
One common theme is friendship. Since they are from different 'worlds' (in the context of the fanfiction), their coming together often leads to the development of a unique friendship. For example, they might learn about each other's strengths and weaknesses and support each other.
In a fanfiction world where Naruto and Rin have a baby, it could be a very interesting story. Maybe the baby would inherit Naruto's positive attitude and Rin's kindness. The story could explore how they raise the child in a world full of challenges and ninjas.
One possible plot could be that Inuyasha and Rin meet in a forest. Rin is now a bit older and has been trained in some basic self - defense skills. Inuyasha is initially cautious around her as she reminds him of his past with Kagome. But as they start to talk, they realize they both have a strong connection to Sesshomaru in different ways. They could end up teaming up to find a lost artifact that has some significance to Sesshomaru's past.
Well, one possibility could be that Rin, with her magical abilities from the Fate series, enters the Harry Potter universe. Maybe she gets sorted into a Hogwarts house, perhaps Gryffindor due to her courage. She could then team up with Harry and his friends to fight against a new dark threat that combines the magic of both universes. For example, a villain who has found a way to use the Grail's power along with dark magic from the Harry Potter world.
One popular inutachi meets rin fanfiction is 'The Encounter'. It has an interesting plot where Inutachi and Rin cross paths in a mysterious forest. Their interaction is really engaging, with Inutachi's curiosity and Rin's gentle nature coming into play.
Kakashi is known for his laid - back yet highly skilled nature. His influence on Naruto could be in terms of teaching him to be more strategic in battles. Rin, being kind - hearted and having a strong sense of care, would give Naruto the emotional support he lacks. So Naruto might become more balanced in his approach to life and ninja - hood.
I'm not sure about the absolute best, but some authors might stand out if they have a deep understanding of both Naruto's and Rin's characters. Those who can capture Naruto's determination and Rin's kindness in their writing would be great. Look for authors who have a lot of positive reviews on fanfiction platforms.