One possible plot could be that after the events of the fourth year, Harry discovers that some of his friends and allies are starting to doubt him because of the return of Voldemort. This makes him feel isolated. He might then start to focus more on self - study of magic, exploring hidden parts of Hogwarts on his own.
Well, perhaps in this fanfiction, the Ministry of Magic spreads false rumors about Harry after the fourth year, like he was in cahoots with Voldemort all along. This causes most of the wizarding community to shun him. So Harry has to find a way to clear his name while being isolated. He could end up staying in a secret place in the Forbidden Forest, where he befriends some magical creatures who help him.
In this 'harry isolated after fourth year fanfiction', it could be that Harry's trauma from the Triwizard Tournament and the return of Voldemort makes him withdraw from his friends. He might feel that he's putting them in danger. So he isolates himself in an abandoned part of Hogwarts, like an old tower. There, he discovers some ancient magic spells inscribed on the walls that he starts to practice in secret, all while trying to come to terms with his new reality.
Hermione could be a main character. She might be one of the few who still believes in Harry and tries to reach out to him despite his isolation. Another could be Dobby. Dobby, being the kind-hearted house - elf, could bring Harry food and supplies while he's in isolation.
Voldemort could still be the main antagonist. Even though Harry is alone, Voldemort would see him as a threat and continue to send his Death Eaters after him. Harry would have to face these attacks all by himself, which would make the story very intense.
In some fanfictions, Harry might become more withdrawn and self - reliant. He could start to question his place in the wizarding world even more deeply, perhaps feeling that he has to face the upcoming threats on his own. He might also begin to explore his magical abilities in isolation, away from the watchful eyes of Hogwarts professors.
One possible storyline could be Harry feeling isolated and betrayed by his friends at Hogwarts. He might decide to go off on his own adventures, exploring parts of the wizarding world that are less known, like some hidden magical forests or ancient ruins.
One idea could be exploring a different version of the Triwizard Tournament. For example, what if there were more magical creatures involved in the tasks? Another could be focusing on Harry's relationship with Sirius during that year in a more in - depth way, like Sirius secretly guiding Harry through some of the tournament challenges. Maybe also a plot where a new student arrives who has a connection to Voldemort's past that no one is aware of and they try to disrupt the tournament.
One possible plot could be that in the afterlife, Harry and Ginny are reunited with all their loved ones who passed away. They might relive some of their most cherished memories together, like their first kiss at Hogwarts. And they could also be involved in some sort of afterlife adventure, perhaps helping lost souls find their way.
One possible plot could be Harry and Ginny settling down and starting a family. They might face challenges like dealing with the after - effects of the war on their mental health. Harry could struggle with PTSD from all the battles and Ginny would be there to support him, while also building her own career as a Quidditch player.
One possible plot could be that Harry and Ginny start their family life. They might face the challenges of raising their children in a post - Voldemort wizarding world. For example, dealing with the legacy of the war and how to teach their kids about it.
One idea could be that Ginny starts to show her true magical potential during their fourth year. Maybe she discovers a new spell that helps Harry in a Triwizard Tournament task. Another plot could be that Harry and Ginny have to work together secretly on a project related to the tournament, and during this time, their feelings for each other start to grow more deeply.
A plot idea could be that Neville is forced by some dark magic to betray Harry. Neville has always been a bit of an outcast and maybe some dark wizard finds a way to use his insecurities against him. He could leak some of Harry's plans regarding the Triwizard Tournament tasks, which would put Harry in great danger.