There's often the sacrifice plotline. They might sacrifice their relationship with Hermione to save a large number of people. For instance, they learn that a dark wizard will spare many lives if they abandon Hermione. Also, the jealousy plotline can exist. If a new character becomes closer to Hermione and they feel left out, they might leave out of jealousy and a sense of not belonging in Hermione's new social circle.
He might cope by focusing on his training. Harry could see it as an opportunity to become stronger without distractions. He would pour all his energy into learning new spells and improving his magical abilities.
Perhaps she tries to find them right away. Using her intelligence and resourcefulness, she starts to search for any clues as to where they might have gone. She could ask other friends, like Neville or Luna, if they have seen Harry and Ron. And she might be determined to bring them back, not willing to give up on their friendship easily.
Sometimes, they get injured accidentally, like in a potions accident gone wrong in the Hogwarts dungeons. This then leads to a series of events where they learn more about each other's vulnerabilities and strengths. It can also bring out the protective sides of their friends, like Harry trying everything he can to make sure they are okay.
If Ron and Hermione leave Harry in the fanfiction, it would change the entire fabric of the story. Harry would have to reevaluate his relationships with other characters. For example, he might turn to Neville for support more often. Also, the power dynamic within the wizarding world could shift. Since Ron and Hermione were important figures in the fight against Voldemort, their absence could give the Death Eaters an advantage, or it could inspire others to step up in unexpected ways. Harry would be forced to grow in ways he hadn't before, and it would be a journey full of self - discovery and new challenges.
One possible reason could be a misunderstanding. Maybe they misinterpreted something Hermione said or did, and in a fit of anger or confusion, they decided to leave. For example, if Hermione was working on a project alone without consulting them, they might have felt left out and left in a huff.
One plotline is that after the rejection, Harry throws himself into his Quidditch or his fight against dark forces even more. Meanwhile, Hermione starts to focus on her own projects and relationships with other characters, like starting a study group with some Ravenclaws. As the story progresses, they might cross paths again and there could be some tension. Sometimes, there could be a plot where Harry starts to develop feelings for another character, like Luna, but still has lingering feelings for Hermione. And the fanfiction might explore how he deals with these mixed emotions.
Another common theme is growth. The characters grow up in the original series, but fanfiction can show even more of their personal growth. Hermione might become an even more powerful witch, Harry could further develop his leadership skills, and Ron might overcome more of his insecurities. This exploration of their individual growth while still maintaining their group dynamic is really interesting in a lot of the fanfictions out there.
One common plotline could be Hermione forming a closer friendship with Fleur. Since she hates Ron, she might turn to Fleur for support and they could end up having adventures together, perhaps in the wizarding world outside of Hogwarts.
Often, Ron might get hurt while exploring a dangerous place like an old wizarding ruin. His friends then have to find a way to get him out safely and also deal with any curses or traps that are activated by his injury. Sometimes, Ron can be hurt by a magical creature too, like a basilisk or a werewolf. This would lead to a race against time to find a cure and also deal with the threat of the creature.
Well, it could be for love. In many fanfics, their relationship has been through a lot, and leaving together is a way to start anew, away from the prying eyes and pressures of Hogwarts and the wizarding community.