Another interesting plot could be a time - travel aspect. What if Harry somehow goes back in time and meets a younger Tonks? They could form an unlikely friendship that changes the course of future events. Tonks could learn from Harry about the future threats and start preparing earlier, and Harry could gain a valuable ally much sooner in his fight against Voldemort.
One idea could be that Tonks gets involved in Harry's search for Horcruxes. Maybe her Metamorphmagus abilities help them in disguising and sneaking into places undetected. For example, she could transform into a Death Eater to infiltrate their meetings and gather information.
One plot idea could be Tonks helping Harry to master some of the more difficult Patronus spells. Since Tonks is a skilled witch, she could offer unique insights and training methods. Another idea is that they go on a secret mission together to find out more about Voldemort's hidden lairs. They might have to use Tonks' Metamorphmagus abilities to their advantage.
One plot idea could be that Tonks uses her Metamorphmagus abilities to help Harry in his undercover missions during the war. For example, she could change her appearance to infiltrate Death Eater strongholds with Harry. Another idea is that Harry discovers a new side of Tonks' personality that he didn't expect, and they bond over their shared experiences of loss. Maybe they both lost someone important to them in the fight against Voldemort and find comfort in each other.
One idea could be that the Hogwarts students are visited by Naruto and his friends. Naruto could show off his ninja skills, like the Shadow Clone Jutsu, which would amaze the wizards. The wizards, in turn, could introduce Naruto to magic like the Patronus Charm. Another plot could involve a common enemy that requires both the power of ninjutsu and magic to defeat. For example, a dark wizard who has also acquired some dark ninja arts.
One idea could be that Naruto is somehow transported to the wizarding world. He might attend Hogwarts and use his ninja skills in the wizarding duels. His chakra could be seen as a unique form of magic there.
One idea could be that the X - Men visit Hogwarts to teach the students about mutant powers and how to co - exist with those who are different. Another could be that Harry Potter discovers he has mutant abilities and has to navigate both the wizarding world and the world of mutants.
One idea could be that the Death Eaters in the Harry Potter world somehow gain access to Hollow powers from Bleach. This could create a new kind of dark magic that the Order of the Phoenix has to deal with. Another plot could involve Hogwarts students being sent to the Soul Society for a special training exchange, and they have to adapt to the different spiritual powers and rules there. And perhaps a powerful Hollows attacks Hogwarts and the wizards have to team up with the Soul Reapers to defeat it.
One idea could be that Tonks discovers a hidden vampire community in the wizarding world while on a mission related to Harry Potter. Maybe the vampires are being wrongly accused of attacking wizards, and Tonks, with Harry's help, tries to uncover the truth.
One idea could be introducing a new character from another universe who accidentally gets transported into the Goblet of Fire timeline. This character could have unique magical abilities that both fascinate and worry the Hogwarts students. For example, they might be able to control time in a different way than Hermione's time - turner. Another plot idea could be that Voldemort discovers a new dark magic spell from this other universe through a mysterious object. This could make him even more powerful and the trio has to find a way to stop him using knowledge from both universes. Also, what if the Goblet of Fire chooses a student from a completely different magical school in this crossover? It would create a whole new dynamic of competition and friendship.
One plot idea could be a crossover where the magical world of Harry Potter collides with the vampire world of Twilight. Maybe Tonks and Alice Cullen team up to solve a mystery that involves both magic and vampire powers. And Tanya could be involved as a sort of rival or an ally depending on the story.
Another plot could involve them being chosen for a special mission by Dumbledore. Because they are the same age and have shown particular skills, Dumbledore thinks they can work well together. They have to travel to a far - off wizarding community to retrieve a powerful magical artifact. Along the way, they face many challenges and their relationship grows stronger.