They might start by gathering information. Harry could use his invisibility cloak to sneak around and eavesdrop on potential suspects. Ron would probably try to contact his brothers who have connections in different parts of the wizarding world for any leads.
Well, Harry has his magical skills and the ability to face dark wizards. He might directly confront the kidnappers if he gets a lead on their location. Ron, with his loyalty and determination, would be right by his side. They could use a combination of spells like the disillusionment charm to approach undetected, and then stun the kidnappers and free Hermione.
Her friends could also play a crucial role. If she has a group of loyal friends, they might band together to find her. They could use their knowledge of the area where she was last seen or any clues they can gather to track down the kidnappers and save her.
Hermione would likely be very angry at first. She is a strong - willed character and being kidnapped would go against all her principles of freedom and rights. She would probably try to reason with Ron immediately, using her logical arguments to make him see how wrong his actions are.
Hermione could use her intelligence to outwit Bellatrix. She might pretend to be compliant and gradually gain Bellatrix's trust, all the while looking for an opportunity to escape. For instance, she could trick Bellatrix into thinking she has some important information that can only be retrieved in a certain location, and then make a run for it when they get there.
Maybe the author wants to explore different relationship dynamics. By having Harry ignore his friends, it creates tension and conflict which can make for an interesting story. It could also be a way to show how fragile their friendship is in certain situations.
Maybe Pepper Potts could find out what Tony has done and rescue Peter. She might be able to talk some sense into Tony and make him release Peter.
It could be Nightwing. He was once Robin himself and has a special connection to the current Robin. Nightwing might hear about the kidnapping and step in to save Robin, using his own unique fighting style and experience.
His friends like Kuwabara and Kurama might also join in the rescue. Kuwabara with his tough fighting spirit and Kurama with his cunning and powerful abilities could be a great help in getting Keiko back from Toguro.
There's also a possibility that Hinata's own clan, the Hyuga, would take matters into their own hands. They have their own unique techniques and a sense of pride. They would not allow the Akatsuki to keep one of their own captive for long and would send their strongest members to retrieve Hinata.
Their relationship could become stronger. They've been through so much together during the war, and now they can fully focus on each other. They might start to understand each other's little quirks even better and have more patience with one another.
In fanfiction, their friendship often develops through shared challenges. For example, when they face a new dark magic threat in the wizarding world, they rely on each other more. Harry's leadership, Ron's humor in tough situations, and Hermione's knowledge combine to make them closer. They also develop their friendship by having deep conversations about their fears and hopes for the future. Maybe Harry shares his concerns about being the Chosen One, and Ron and Hermione support him wholeheartedly.