A common plotline could be that they meet in a secret place in Hogwarts, like a hidden room. They discover they both have secrets they can't share with others easily. For example, Daphne might be involved in some kind of research on a rare magical plant, and Harry could be having some strange dreams about Voldemort again. They bond over their need for secrecy.
Another plotline could be that they meet through mutual friends. Maybe Hermione is friends with Daphne in this fanfic world. Hermione sets up a meeting between them, thinking they might get along. At first, they're a bit awkward, but then they find out they both love exploring the Forbidden Forest (in a safe way, of course). This shared interest brings them closer together.
Often, they meet due to a common mission. Let's say there's a threat to the wizarding world that requires both of their skills. Daphne is known for her intelligence in potions and magic theory, and Harry for his bravery and experience in fighting dark wizards. So they team up, and during their adventure, they start to fall for each other.
A common plotline is that Daphne saves Harry from a dark magic attack. For example, she might notice a cursed object meant for Harry and intervenes just in time.
One possible plotline could be that they meet in the library while searching for a rare book. Harry might be looking for something to help him with a difficult class assignment, and Daphne could be researching dark magic for a different reason. They start off as rivals in this search but gradually develop a mutual respect and then friendship that could potentially turn into something more.
Well, they could start off by being quite surprised to see each other. Maybe they meet in the library at Hogwarts. Harry might be looking for a book on Defense Against the Dark Arts and Daphne could be there studying potions. They could exchange a few words, like Harry asking Daphne if she's seen a certain book. And then they might realize they have more in common than they thought.
In the fanfic, it's possible that they are both there on a secret errand. Harry could be looking for a hidden magical item that he believes is stored in Gringotts for safe - keeping. Daphne might be there under orders from her family. When they meet, they might initially be guarded about their true purposes. However, as they interact, they start to trust each other and decide to collaborate, which could set off a whole new chain of events in the story.
One interesting plotline could be them discovering a hidden family secret together. Maybe they find out that their family has a long - lost magical heirloom that holds great power. They would then embark on a journey to learn more about it and protect it from those who would misuse it.
One interesting plotline could be their adventures at Hogwarts together. They might study for exams in the library, and Harry could discover new spells with Daphne's help. Another could be them facing challenges like the Triwizard Tournament side by side.
One common plotline is that Daphne witnesses something she shouldn't, and Harry has to use Obliviate to protect her. Another is that an enemy uses Obliviate on Daphne to make her forget her connection to Harry, causing a rift between them. And sometimes, Harry accidentally obliviates Daphne's memories related to their relationship, and he has to find a way to make her fall in love with him all over again.
One interesting plotline could be how Harry and Daphne initially react to the marriage contract. Maybe Harry is hesitant at first, but as he gets to know Daphne better, he starts to see the potential in their relationship. Another could be the challenges they face from their families and society due to the contract.
One interesting plotline could be their exploration of the secrets within the House of Black. Maybe they discover long - lost magic or family heirlooms. Another could be their relationship development against the backdrop of the complex Black family politics.
Another plot could involve Daphne Greengrass being a secret admirer of Harry Potter from afar. As the story progresses, she gradually reveals her feelings and they start to bond over their shared experiences of the wizarding world, like dealing with the expectations of their pure - blood families.