Perhaps the story could be about Harry coming to live with Haruhi in her world. He'd be adjusting to a completely different lifestyle. He could introduce some of his own unique skills and knowledge, like his knowledge of potions (again, from the Harry Potter world) which he could use to create unique drinks for the Host Club. And of course, there would be a lot of sibling bonding moments as they navigate their new relationship in this strange new setting.
Well, the plot could revolve around family secrets. Maybe Harry discovers that their family has some sort of special heritage that ties into both the world he comes from and Haruhi's world. They could go on a journey together to uncover the truth about their family, all while Haruhi is still dealing with her school life and the Host Club. Harry might have to protect Haruhi from some threats that are related to this family secret.
At first, it might be a bit awkward. Since they likely grew up apart or in different situations. But as they spend more time together, they'd start to understand each other better. They could share their problems, like Haruhi talking about her financial struggles and Harry sharing his experiences with the wizarding world's challenges.
The plot could also involve Harry and Bella's joint adventures. They could team up against common enemies that might emerge from the combination of the two fictional universes. Harry might use his knowledge of magic and Bella could use her understanding of the vampire - werewolf politics in Forks. They could also face challenges within their family, like how their parents react to the strange things happening around them.
Well, one possible plot could be that they discover their brotherhood in a mysterious way. Maybe they start having strange dreams or visions that lead them to find each other. Then they could combine their powers, Harry's magic from the wizarding world and Tsuna's combat skills from his own world, to fight a common enemy.
One possible plot could be that they discover their brotherhood through some sort of magical or ninja - related mystery. Maybe there's a hidden prophecy or an ancient artifact that reveals their connection. Then they have to team up to face a common enemy that threatens both their worlds, like a dark wizard - ninja alliance.
One possible plot could be that Harry, being Voldemort's little brother, has been hidden away from the wizarding world by some powerful magic. As he grows up, he starts to discover his true identity and his connection to Voldemort. This discovery throws the wizarding world into chaos as they don't know whether to trust Harry or see him as a threat.
One possible plot could be that Harry discovers this long - lost family connection after some mysterious event. Maybe he finds a hidden letter or an old family heirloom that reveals the truth. This discovery could throw him into an identity crisis as he has to come to terms with being related to a Death Eater. He might then try to find out more about his family's past and his connection to Bellatrix, which could lead him into dangerous situations as he delves deeper into the dark secrets of his family.
One possible plot could be that Harry discovers his true identity as Superman's brother. He might have been separated from Superman at birth for some reason, like a threat to their family. Then, as he grows up in the wizarding world, he starts to show some superhuman abilities which he doesn't understand at first. Eventually, through a series of events, he meets Superman and they realize their connection. Together, they use their combined powers of magic and super - strength to fight a common enemy that threatens both the wizarding world and Metropolis.
One possible plot could be that Harry discovers his long - lost brother Carlisle. This could lead to a journey where Harry has to adapt to the vampire world that Carlisle is part of, while also bringing his own magic into it. Maybe they team up to fight against a common enemy.
In this fanfiction, the plot might be that their brotherhood is a key to uniting two different factions. Harry could represent one side and Uryu the other. Their bond as brothers becomes a symbol of hope for the two groups to come together and cooperate. Along the way, they face internal and external challenges, like people who oppose their union and those who want to use their relationship for their own gain. There could also be a sub - plot about them learning about each other's cultures and abilities, which helps them grow as individuals and as brothers.
One possible plot could be that Harry Potter, with his magic skills, accidentally stumbles into the world of Haruhi Fujioka. He notices that Haruhi is in some sort of trouble at school, perhaps with some mean students. Harry uses his magic to play some harmless pranks on those students to teach them a lesson. Then he starts to help Haruhi with her various club activities in a magical way. For example, he could use magic to make the common room of the host club look even more amazing for an event.