Lucy would be a bit scared at first. She's used to dealing with magical creatures within the Fairy Tail world, but Ghost Rider is something entirely different. However, her curiosity would soon get the better of her, and she'd start asking questions about his powers and origin. Happy would probably hide behind Natsu, peeking out nervously. As for Wendy, she might be in awe of Ghost Rider's power, but also concerned about the potential danger he poses to her friends.
Ron would likely be more on the scared side at first. He'd be hesitant to get too close to the Ghost Rider, but as he saw the Ghost Rider using his power to fight against dark forces, he might start to respect him. Ron would probably crack some jokes along the way to ease the tension, like comparing the Ghost Rider's flaming head to a really over - the - top Weasley's Wizard Wheezes product.
The Hashiras would likely show concern. Some, like Shinobu, would immediately start looking into possible medical solutions. Giyuu might be more reserved in his worry but would still keep a close eye on Tanjiro. The other demon slayers would also be affected. They look up to Tanjiro, so his sickness would lower the morale of the group. They would try to support each other while waiting for Tanjiro to recover.
Issei would probably be both scared and excited. He's used to dealing with powerful beings, but the Ghost Rider is on a whole different level. He might initially try to fight him out of bravado, but soon realize he's outmatched. Rias would be more cautious. She would see the Ghost Rider as a potential threat to her peerage and would try to figure out his motives before taking any action.
Hero characters might analyze it from a moral perspective. They could either approve or disapprove of the way the story is told in the fanfiction depending on whether it aligns with their sense of right and wrong. Villain characters, on the other hand, might look for ways to use the ideas in the fanfiction to their advantage, like new ways to create chaos.
The Death Eaters would likely be both scared and intrigued. They might see the Ghost Rider as a potential new weapon or a threat to their own dark plans. Voldemort himself would probably view the Ghost Rider as a rival in terms of power. He might try to either destroy the Ghost Rider or subjugate him. The other wizards in the Ministry of Magic would probably panic and try to contain the situation without really understanding what they are dealing with.
The story of Ghost Rider involves a person who becomes possessed by a supernatural spirit and gains supernatural powers to seek vengeance against evil. It's a tale of redemption and justice in a dark and supernatural world.