Dobby, if he is still alive in the fanfiction, could play a very important role. He could bring her things she needs, like fresh clothes or healing potions. He's very loyal and would do anything to help Hermione recover. The goblins might also be important. They could offer some unique magical items or knowledge that aids in her healing process.
In some fanfictions, when Hermione starts to regain her strength, she might have a small moment with Harry or Ron. For example, Ron bringing her some of her favorite books that were salvaged. It's a simple gesture but it really shows their friendship and how they are there for her during her recovery.
Love and relationship development is a very common theme. Since Shell Cottage is a relatively private and peaceful place, it's a great setting for Ron and Hermione to explore their feelings for each other further after all the chaos of the war.
Well, Naruto is the key figure in these fanfictions. But characters like Tsunade can't be ignored. As the Hokage, she may give Naruto special tasks or resources that aid in his rise. Rock Lee is also common. His dedication to training and his unique fighting style can inspire Naruto. And Neji, before his death in the original series, could be a character who, in fanfiction, has a change of heart and helps Naruto understand more about the Hyuga clan's secrets, which in turn helps Naruto gain more power and influence.
It could be a Death Eater who has managed to infiltrate Shell Cottage. Hermione might stab in order to stop the Death Eater from harming her friends or stealing important information.
Well, obviously Harry himself is the central character. But aside from his friends, characters like Draco Malfoy could have a different relationship with Harry. Instead of being just a rival, he could be an ally of sorts in Harry's dark journey, or perhaps he tries to use Harry's newfound darkness for his own gain. Snape too could be important. Given his complex relationship with Harry, he might be in a position where he has to choose between helping Harry return to the light or letting him continue down the dark path.
Sasuke is often important. If Naruto goes back in time, Sasuke's story might be greatly affected. Naruto might try to prevent Sasuke from going down the dark path he once did.
Well, it could be a story where Hermione is in a dangerous situation at Shell Cottage. Maybe she's being attacked and has to use a stabbing motion in self - defense. It might involve dark wizards or some other threats.
It could be Death Eaters. They are always on the hunt for Harry and his friends. If they manage to find Shell Cottage, they might see Hermione as a major threat and use a deadly spell on her.
His friends are very important. Rukia, for sure. She has a lot of knowledge about the spiritual world and could be the one to figure out what's wrong with Ichigo. Orihime with her healing powers also plays a big role. She might use her abilities to ease his pain or at least keep his condition from getting worse. Uryu could also be important as he might use his Quincy skills to analyze what's causing Ichigo's sickness.
One great piece of Ron and Hermione Shell Cottage fanfiction is 'A Moment at Shell Cottage' which beautifully depicts their tender moments there. It really delves into their relationship post - war in the idyllic setting of the cottage.