The Hokage at the time, whether it's Tsunade or someone else, would likely get involved. They would allocate resources and ensure that the best medical care is provided. Additionally, some of the older ninja who knew Kakashi since he was young, like Iruka, might offer moral support and assist in any way they can, like gathering information or running errands related to his treatment.
Another scenario could be in a mission gone wrong. The fanfiction might depict a mission where Naruto and his team are caught off - guard by an ambush. There could be a large number of well - coordinated enemies, and Naruto might end up being the main target, getting severely injured as he tries to fight them off and protect his team.
Even some of the antagonists could potentially help Jaune if there is a complex relationship developed in the fanfiction. For example, if an enemy realizes that Jaune's death or continued injury would disrupt some sort of balance, they might step in to heal him, albeit reluctantly.
Sasuke is very likely to be involved. Given their complex relationship, Sasuke could be the one who finds Naruto severely injured and has to make a choice between helping him or leaving him. Another character could be Sakura. As a medic - ninja, she would be the one to try and heal Naruto's severe injuries. Kakashi too might be involved, either as a mentor figure who tries to figure out what happened to Naruto or as someone who has to step in to protect Naruto from further harm while he is injured.
Bobby could also be a key figure. He's like a father figure to the boys and has a wealth of knowledge. He might know of some old remedies or be able to point them in the right direction to find a way to heal Dean. Charlie could also pitch in. She's smart and resourceful and could use her hacking skills to find information related to Dean's injury.
One common plot development could be his comrades rallying around him. For example, Naruto might be determined to find a way to heal him quickly, using his newfound powers or connections. Another could be Kakashi reflecting on his life while injured, thinking about his past mistakes and how he can grow from them if he recovers. Maybe he also has some sort of vision or encounter with a long - lost friend or relative in his weakened state.
His teammates are very likely to help. Kagami, for instance, might push him during rehabilitation exercises in a tough - love kind of way. The other members of Seirin could also offer moral support, like bringing him his favorite snacks or just spending time with him. His coach too could be involved, providing expert advice on how to come back stronger.
For Kakashi, a character like Naruto could potentially cause jealousy in some fanfictions. Since Naruto and Sakura are very close friends, if Sakura spends a lot of time with Naruto on a mission or training, Kakashi might feel a twinge of jealousy. He might wonder if there are deeper feelings between them. As for Sakura, a new female sensei in the village could make her jealous. If this sensei is very attractive and Kakashi seems to respect her a great deal, Sakura could start to feel envious.
Venom could be another one. He has a vendetta against Spiderman, and knowing he's injured, he would likely try to finish him off once and for all. He could lurk in the shadows waiting for the right moment to attack.
The main characters would most likely be Naruto, Kakashi, and the other genin participating in the Chunin Exams. Naruto is central to the Naruto series, and his performance in the exams is always a big focus. Kakashi, as his sensei, would play an important role in guiding and protecting him. The other genin like Sasuke, Sakura, and the various opponents from other villages are also likely to be main characters as they are key to the drama and action of the Chunin Exams.
The other dragon riders could also be in the fanfic. Fishlegs could use his knowledge of dragons and other lore to figure out if there's a dragon - related way to heal Astrid. Snotlout might initially seem more concerned with his own status but would probably end up helping in his own way, perhaps by providing some muscle when needed for tasks related to Astrid's care.