Another idea is that Harry is alone because he's being targeted by Death Eaters who see the tournament as an opportunity to get to him. With Dumbledore seemingly preoccupied, Harry has to face these threats alone. He might start to doubt his place at Hogwarts and wonder if he should just leave to keep everyone safe.
One possible storyline could be Harry feeling isolated as he prepares for the Triwizard Tournament without much support from his friends. Maybe Ron is jealous and Hermione is too busy with her own studies. So Harry has to rely on his own skills and instincts more, like when he's figuring out the clues for the tasks.
Perhaps Harry is alone because he's keeping a big secret during his fourth year. He discovers something about Voldemort or the tournament that he doesn't want to share with anyone yet, not even his closest friends. This secrecy makes him pull away from others, and he spends a lot of time in the Forbidden Forest or other secluded places at Hogwarts, trying to figure things out on his own.
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.
Well, a common storyline could be that Harry, after being abandoned by his parents, is discovered by a powerful but reclusive wizard. This wizard takes Harry under his wing and trains him to be extremely powerful in magic, much more so than in the original story. This could lead to Harry having a different set of friends and enemies. Another idea is that Harry is abandoned near a magical school in another country. He grows up there, learning a different type of magic. When he finally comes to Hogwarts, he has a clash of magical cultures. And yet another could be that Harry is found by a magical organization that experiments on abandoned magical children. He has to escape from there and then find his true identity and place in the wizarding world.
Well, since Harry is alone, he might view Cedric as more of a rival than he would if he had his friends around. He could be more suspicious of Cedric's motives in the Triwizard Tournament. Maybe he doesn't trust Cedric as much and is constantly on guard around him.
One possible storyline could be that Harry is adopted by a kind wizarding family. They raise him with love and he grows up having a different kind of magical upbringing. He might learn different spells and magical traditions from what he would have at the Dursleys. Another could be that he ends up in an orphanage in the wizarding world, where he makes friends with other magical orphans and they form a sort of found family. They all look out for each other and together they discover secrets about Harry's past that his parents might have left behind.
Another idea is that some Death Eaters find Harry without his glasses in a vulnerable state. They start by taunting him about his weakness without the glasses. Then they use dark magic to make him experience extreme pain, like a searing pain in his eyes as if they are trying to make him feel the 'punishment' for relying so much on his glasses. They might also try to force him to perform difficult magic tasks without being able to see clearly, and punish him severely when he fails.
One possible storyline could be that Harry grows up in isolation in the cupboard under the stairs, with no real interaction with other wizards or even muggles his age. He might develop his magic skills in secret, and when he finally enters the wizarding world, he has a very different perspective compared to the original story.
One possible storyline could be Harry struggling with PTSD from the war. He might isolate himself in Grimmauld Place, haunted by the memories of those he lost. Another could be him trying to find a new purpose in life, perhaps traveling the wizarding world alone to discover forgotten magic. Or he could be dealing with the public's perception of him as the 'Chosen One' and feeling the pressure to always be strong and heroic.
One possible storyline could be the challenges they face in preparing for the baby. For example, they might struggle with finding a suitable place to live as a family. Another could be how their families react. Harry's wizarding friends might be very excited and offer all kinds of magical help, while Padma's family in the wizarding world could have different cultural expectations.
One possible storyline could be Ginny having to hide her pregnancy from the enemy to protect herself and the unborn child. She might rely on the help of her closest friends and family to stay safe.
In this fanfiction, Harry could be alone because he feels estranged from his friends who have moved on with their lives in different ways. So he takes on a solitary mission to protect the wizarding world in the shadows. He becomes a sort of unseen guardian, constantly thwarting small threats that could potentially grow into big problems, all while dealing with his own loneliness and the memories of the war.