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.
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.
Deku might be completely shocked at first. Since Bakugou has always been so aggressive towards him, he would never expect such a confession. He might just stand there, mouth agape, not knowing what to say.
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.
He might cry a lot. Deku is very emotional, and being cheated on would be a very painful experience for him. He could also get angry, which is rare for him, but this situation would be so unjust that he might not be able to hold it in. He'd probably start to question his self - worth too, thinking that there was something wrong with him that made his partner cheat.
Deku might be initially shocked. He's used to Bakugou's aggression, but an actual injury is different. He could be in pain and disbelief at first. Then, he might try to downplay it, especially if he doesn't want to cause trouble for Bakugou, because Deku is generally a very forgiving character.
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.
Well, some might be really amazed. They could see a new side of Deku that they never knew before. His singing might show a different level of confidence or a hidden talent, so they would probably cheer him on.
Some characters might try to understand Deku's motives. Kirishima, who was close to Bakugou, would be angry at first but might also try to find out if there were any extenuating circumstances. However, many would be afraid of Deku, seeing him as a threat now that he has killed one of their own.