Harry often tries to be there for her. He might not fully understand her depression at first, but he'll stay by her side, offer a listening ear and try to cheer her up in his own clumsy way, like suggesting they go on an adventure or something.
Harry would probably be extremely worried. He'd immediately rush to her side, trying to figure out how to help. Ron, on the other hand, might be in a bit of a panic at first but then would do whatever he could to protect her while waiting for help. Hagrid might bring some of his home - made remedies, thinking they could work on her injury.
Well, Harry might be a bit surprised at first. But he could also be supportive as he values both Sirius and Hermione. He might see that Sirius makes Hermione happy and be okay with it.
Harry would be extremely worried. He'd probably rush to her side immediately and try to do whatever he can to help. He might blame himself for not being there to protect her. Ron, on the other hand, would be in a state of shock at first and then would try to use his humor to lighten the situation a bit while still being very concerned. Hagrid would be devastated. He sees Hermione as one of his students he cares about, and he'd likely bring some sort of magical creature - related remedy, thinking it could help.
Well, the other students in Gryffindor would likely be a bit taken aback at first. But then, knowing Hermione's intelligence and her tendency to be different, they would probably accept it. They might be curious about how she's going to manage to keep up the charade. The Hufflepuffs would be generally kind and understanding, perhaps even offering to help her if she needs it. The Ravenclaws would be intrigued by the idea and might study her transformation from a more academic perspective. The Slytherins, as a whole, would be more likely to try and use her disguise against her, either by blackmailing her or trying to expose her in a way that would cause her and her friends embarrassment.
The other Robins would be in shock and disbelief. Dick Grayson might try to comfort the others while also feeling a deep sense of loss as he was like a big brother to Tim. Damian Wayne, on the other hand, might initially hide his feelings but then become more aggressive in his pursuit of justice for Tim's death.
Naruto would be extremely devastated. He sees Kakashi as a mentor and father figure. He might go into a period of deep depression at first, but then turn his grief into motivation to become stronger. Sakura would also be very sad and might focus more on her medical skills, vowing to save more lives in Kakashi's memory. Sasuke might have a more internal reaction, feeling guilty if Kakashi died protecting him, and it could further fuel his own goals, whatever they may be at that time.
The village elders would also be concerned. They might start to think about the future of the village without Naruto. Some might even start looking for a temporary replacement for him as Hokage, which could cause some internal conflict in the village as not everyone would agree on who should take over.
Other characters' reactions can vary widely. Some of the more empathetic classmates, like Tsuyu, might offer words of comfort and stay by his side. Mineta might be a bit more cowardly, but still show some concern. The teachers, such as Aizawa, would take charge of the situation. Aizawa would ensure Midoriya gets proper medical attention and also start an investigation if the injury was due to foul play. His mother, if she were to find out, would be extremely worried and rush to be by his side as soon as possible.
Hermione would probably be the first to notice the signs of abuse. She'd be very methodical about it, perhaps making a list of all the things that seem off. Ron, on the other hand, would be more impulsive. He might get angry right away when he realizes what has been happening to Harry. Dumbledore, being the wise figure, would likely start to put plans in motion to protect Harry and also to deal with the source of the abuse.
Harry would probably be very surprised and a bit concerned. He's always been protective of Hermione, and this sudden turn of events with Draco would make him wonder what's going on. Ron would likely be more openly shocked and perhaps a bit jealous. He has had his own complicated feelings for Hermione over the years.