Well, perhaps in the fanfiction, the marriage contract is tied to some ancient magic that needs to be fulfilled for a greater good. Harry and Cho start off on the wrong foot because of it. But as they explore the terms of the contract, they discover secrets about their families and Hogwarts. They might also face opposition from other characters like Hermione who think it's a bad idea.
In this fanfiction, a possible plot could be that the marriage contract is activated during a dangerous time at Hogwarts. Harry and Cho are forced to come together to protect the school and the wizarding world. Along the way, they learn about each other's fears and dreams. Cho helps Harry deal with his post - war trauma, and Harry gives Cho the confidence she lacked after Cedric's death. As they fulfill the requirements of the contract, they gradually fall in love.
One idea could be that the marriage contract was made by their families long ago without their knowledge. Harry initially resists but then realizes Cho has some qualities he admires. Another could be that the contract is a magical mistake and they have to work together to figure out how to break it while dealing with their feelings for each other.
One idea could be the cultural and family clashes that come with such a contract. Maybe Harry's friends are shocked and have mixed reactions. Another could be how Harry and Tonks grow to understand and care for each other in the context of this contract. For example, they start off as strangers in this arranged - like situation but gradually find common interests.
The main characters are obviously Harry Potter and Cho Chang. Harry is the famous wizard who defeated Voldemort, and Cho is his classmate who he had a bit of a romantic history with in the original books.
One interesting idea could be the complex relationship dynamics that develop due to the marriage contract. For example, Harry might have to navigate new social expectations and deal with characters who have different motives regarding the contract. It could also lead to unexpected alliances or rivalries within the wizarding world.
Perhaps in this fanfiction, Harry bought Cho's contract to get closer to her. He might have feelings for her still and this is his rather strange way of showing it. Then they could start to work together on something, like fighting against a new threat in the wizarding world. As they spend time together due to the contract, their relationship could either rekindle or they could just become really good friends.
In some 'harry potter and cho chang harem fanfiction', there could be a plot where an ancient magic is involved. Cho Chang discovers that she has a special connection to this magic, and the other members of the harem, including Harry Potter, must help her control it. This could lead to adventures outside of Hogwarts, like exploring ancient wizarding ruins, and during these adventures, their relationships would deepen and develop in various ways.
One idea could be that Naruto unknowingly signs a marriage contract with multiple girls due to a prank by a mischievous character. Then he has to navigate through the awkwardness and growing relationships with each of them. For example, Sakura might be initially angry but then realizes her true feelings for Naruto through this situation. Another could be that the marriage contract is part of an ancient prophecy and Naruto has to fulfill it to save the village, which leads to him getting closer to Hinata, Ino and other female characters in different ways.
One interesting plot point could be how Harry and Severus initially react to the marriage contract. Maybe Harry is shocked and resistant at first, while Severus is more resigned to it due to his sense of duty.
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.
A possible plot twist is that the marriage contract potion gets mixed up with another potion. So, instead of creating a marriage - bound situation, it creates a situation where the characters have to work together to reverse the wrong potion's effects. This could lead to all sorts of adventures and self - discovery for the characters as they figure out how to fix things.
One interesting plot twist could be that the marriage contract was actually a ruse by a dark wizard to gain control over both Harry and Fleur. So they have to team up to break the contract's hidden enchantments.