One way could be through a magical mix - up. Maybe a dark wizard, in an attempt to control Harry or Bellatrix, forges a marriage contract long forgotten. Harry, upon discovering it, might initially be horrified as Bellatrix is a Death Eater. But as the story progresses, he could see it as a way to infiltrate the Death Eaters from the inside. Bellatrix, on the other hand, might see Harry as a powerful asset. So the plot could develop with a lot of power plays and mind games between them.
One way could be through a time - travel or alternate reality plot device. Maybe in a world where dark and light magic collide in unexpected ways, Harry and Bellatrix are forced to work together and somehow, against all odds, a connection forms that leads to a child. It would be a very complex relationship, full of inner turmoil for both characters.
One possible plot could be that Harry and Tracey enter into a marriage contract for convenience. Maybe Harry needs to inherit something and being married to Tracey is a condition. They start off as strangers but gradually get to know each other through the requirements of the contract. They face challenges from their families who initially don't understand their motives.
One common theme is the struggle against pre - determined fate. Since the marriage contract is something they didn't choose, both Harry and Bellatrix often struggle to come to terms with it. Another theme is the exploration of dark and light magic. Bellatrix is associated with the dark side, and Harry with the light, so their union makes for an interesting exploration of how these two types of magic can interact.
One possible plot twist could be that the marriage contract was actually a ploy by an enemy to divide their wizarding families. Maybe the terms of the contract were misinterpreted at first, and as they start to fulfill it, they discover hidden clauses that put them in a difficult situation.
Hermione would be extremely shocked and worried for Harry. She would see it as a dangerous situation and would try to find a way to break the contract through research. Ron would probably be more vocal about his disbelief and might even make some jokes about it at first, but then he'd also be concerned for Harry's safety. Dumbledore, being the wise figure, would see it as an opportunity to gain an edge over Voldemort. He would try to guide Harry on how to handle Bellatrix while being in this contract situation.
One popular 'Harry x Bellatrix Marriage Contract Fanfiction' is 'The Unforeseen Bond'. It delves into the complex relationship that forms due to the marriage contract. It shows how Harry and Bellatrix are forced to interact and gradually understand each other in a world full of magic and political intrigue.
The fanfic could also have a more romantic - themed plot without the marriage contract. Harry and Daphne meet in an unexpected place, like the Forbidden Forest. They initially distrust each other but then find out they both have a love for exploring the unknown areas of magic. As they start to share their knowledge and experiences, a bond forms between them. They go on adventures together, from exploring hidden chambers in Hogwarts to traveling to other magical places, and their relationship blossoms into a deep, loving one.
Well, perhaps the marriage contract was made with an evil wizard. Fleur has to figure out a way to protect herself and her family. She teams up with some of the Order of the Phoenix members who are also interested in the ancient magic involved in the contract. They research in the Hogwarts library and other secret places to find a way to nullify the contract. In the process, Fleur also has to deal with the wizard who is trying to enforce the contract and his minions. This could lead to some exciting battles and tense moments.
In a 'Harry and Susan Marriage Contract Fanfiction', a possible plot point is how they deal with their own personal goals. Harry might have his own heroic or magical pursuits, and Susan could have her own dreams. The marriage contract could either support or conflict with these goals. And then there's the aspect of friendship. How do their existing friends react to this sudden marriage contract? Do some friends try to break them apart, or do they help them make the best of it? That can add a whole new layer to the story.
He'd probably be shocked. Harry has always been a bit independent when it comes to relationships. He might feel trapped at first.