Well, it can be considered popular. It has a certain following. The world - building in 'ragna crimson light novel' is really appealing, which is one of the reasons for its popularity. Also, the character development is engaging, making readers want to keep reading to see how the characters grow and change throughout the story.
Yes, there might be. Fanfiction platforms are filled with all kinds of creative crossovers. You can start by checking major fanfiction websites like Archive of Our Own or FanFiction.net. Just search for the keywords 'Naruto' and 'Ragna the Bloodedge' in their search bars, and you may find some interesting stories that combine these two characters in unique ways.
Perhaps Naruto is reincarnated as Ragna the Bloodedge. He would have Ragna's memories but also his own ninja skills and values. This could lead to him trying to change the fate of Ragna's world. For example, he could use his Naruto - style persuasion to unite some of the warring factions in BlazBlue. He might also introduce some of the ninja techniques to that world, creating a whole new dynamic in battles and relationships. Since Naruto is known for his growth and development, he could also change Ragna's character arc in unexpected ways.
Friendship is a common theme. Since they are paired in the fanfic, their relationship often develops into a strong bond of friendship as they go through various situations together.