Dumbledore would feel a great sense of loss and guilt. He had always seen Harry as the key to defeating Voldemort. His reaction could be to go into seclusion for a while to think about what went wrong. The other Hogwarts professors would be in shock. Hagrid would be heartbroken and might even leave Hogwarts in his grief. And the Death Eaters would be jubilant, but also a bit wary as they know that there could be unforeseen consequences to Harry's death.
Ron would be completely shattered. Harry was his best friend, and he would likely feel guilty for not being able to protect him. He might become reckless in his attempts to avenge Harry. Hermione would be grief - stricken but also determined. She would pour herself into finding a solution to the mess left behind. Ginny would be heartbroken. She might initially withdraw but then become a strong advocate for justice, using her own skills and magic to fight against Voldemort's regime.
Ron and Hermione would be completely shattered. Ron, who had been Harry's friend since the beginning, would probably be in denial at first. Hermione would likely try to figure out what exactly happened. Dumbledore would be solemn and would try to keep the school calm while also investigating the matter. Hagrid would be inconsolable, crying his eyes out. The other students would be in a state of shock and sadness. The teachers would also be deeply affected, especially those who had taught Harry or had some connection with him.
The characters in 'Naruto' would be deeply affected if Naruto dies at birth in fanfiction. Jiraiya would be one of the most affected. He saw Naruto as his protege and the hope for the future. Without Naruto, Jiraiya might lose his enthusiasm for training and spreading his teachings. Tsunade would also be saddened as she had a connection to Naruto through her relationship with Jiraiya and Minato. The Rookie 9, Naruto's friends, would have a completely different dynamic. They might not form as tight a group without Naruto's energetic and positive influence. And the Sannin, as a whole, would have their relationships and legacies altered without Naruto in the picture.
Rias would be devastated. Issei was not only her servant but also someone she had deep feelings for. She would likely go into a rage at first, vowing to find and punish whoever was responsible. Akeno would be heartbroken as well. She and Issei had a special bond, and she would be in mourning for a long time. Kiba might feel a sense of guilt, wondering if he could have done more to protect Issei. Asia would be in shock and constantly pray for Issei's soul, hoping for some kind of miracle.
Harry would be crushed. He'd feel like he lost a sister. Ron would be in total despair, probably blaming himself. Ginny would be heartbroken too as Hermione was like a sister to her. The Weasley family, who had accepted Hermione as one of their own, would be in mourning. They'd all wonder how they could have prevented it and would be angry at the unfairness of it all.
The wizarding world would be in shock. People who once saw Harry as their savior would feel betrayed. The Order of the Phoenix would be in disarray, not knowing whether to try to rescue Harry or consider him an enemy. Hogwarts would also be in turmoil, with students and teachers alike not believing that Harry could turn to the dark side.
Hermione, on the other hand, would likely have a more critical view. She'd analyze the fanfictions for their accuracy in terms of magic lore and Hogwarts traditions. If there were any inaccuracies, she'd be quite perturbed. However, she might also appreciate the creativity that goes into some of the well - written ones that add new dimensions to their magical world.
Tsunade herself would be in a state of shock and deep remorse. She might blame herself for Naruto's death, thinking that she should have been stronger and not needed saving. The villagers would also be greatly affected. The children who looked up to Naruto as a hero would be heartbroken. They would start to tell stories about his bravery, and some might even be inspired to become like him, despite his tragic end.
Bakugo would be deeply affected. He might initially deny his feelings, but then would be filled with guilt for all the times he was mean to Deku. He could become more withdrawn and focused on becoming a hero worthy of Deku's sacrifice.
Sakura would be heartbroken. She would probably blame herself for not being able to protect Naruto. She might also start to train harder to fill the void left by Naruto.