The main characters are Yuma and Dark Mist. Yuma is likely to have certain unique abilities or characteristics that make them an interesting protagonist. Dark Mist, on the other hand, probably has an air of mystery about it, with powers that are either dark - in the sense of being related to shadows or the unknown - or powers that are misunderstood as being dark.
In this fanfiction, Yuma is surely one of the main characters. He might be a hero - type figure with courage and determination. Dark Mist, which could be a spectral or shadowy being, is also a main character. Their relationship is the focus, whether it's a friendship, an alliance, or something more complex. Their interactions will drive the story forward.
One idea could be that Yuma and Dark Mist are from different realms and they accidentally meet. They initially have a misunderstanding but as they get to know each other, they find they have a common goal of protecting a certain magical artifact. Another could be that Dark Mist is being hunted and Yuma offers protection in exchange for knowledge about a mysterious power.
One possible fanfiction could be about Yuma and Dark Mist forming an unexpected alliance. Maybe Dark Mist has some hidden motives that initially seem malicious but as the story progresses, it turns out he's actually trying to protect Yuma from a greater evil in the Zexal world.
I'm not certain as I don't have specific knowledge about this fanfic. But it could be characters from the Yuma universe that are related to the x - ray aspect, perhaps a scientist character who is studying x - rays.
I'm not entirely sure, but it could be some of the survivors from the original 'the mist' story. They might have different personalities and skills that are further explored in the fanfiction.
The main characters are the escort and the criminal. The escort is a man who has been tasked with taking the criminal to the 3:10 train to Yuma. The criminal is a character who is trying to avoid being sent to Yuma and will do whatever it takes to escape from the escort.
In the '3 10 to Yuma original story', the two key characters are the rancher and the criminal. The rancher is a regular guy, probably facing his own financial and family problems on his ranch. But he has a sense of justice that makes him take on this dangerous job. The criminal, on the other hand, is a complex figure. He's likely done some really bad things but also has his own charm and intelligence. He will try everything he can to escape from the rancher's custody during their journey to Yuma.
Since we don't have the details of the story, it's difficult to say exactly. However, it might be a group of outlaws trying to escape from the '310' region and find refuge in Yuma. Or it could be a family who has to relocate from '310' to Yuma for some reason like a job opportunity or to escape a difficult situation back in '310'.
Since the title only mentions Sakura, she's likely to be one of the main characters. But there could be others, like the prison guards or fellow inmates. Maybe there's a character who befriends Sakura or an antagonist who makes her life difficult in the prison.
Kakashi could also be a main character in certain 'naruto red mist fanfiction'. His experience and knowledge could be important in figuring out the mystery of the Red Mist. He might be mentoring the younger characters on how to handle the new threats and challenges that the Red Mist brings.
Obviously, Sakura is one of the main characters. In many such fanfictions, there could also be characters like Naruto and Sasuke who interact with Sakura in different ways due to her being from the Hidden Mist. Maybe Kakashi could also be involved to mentor or guide her.