In such a fanfic, perhaps Ginny uses some kind of magical coercion. Maybe she has found a powerful spell that bends Harry's will just enough to make him agree to the marriage. It could also be that she manipulates a situation where Harry feels he has no other choice but to marry her, like threatening to expose a secret of his that could harm his reputation.
Well, it might be that Ginny is under some external influence herself. For example, a dark force could be making her act this way. She could be possessed by a dark entity that wants to control Harry through marriage. Or, in the fanfic, Ginny might be desperate because she's afraid of losing Harry to someone else. So she resorts to forcing him into marriage, thinking it's the only way to keep him.
The plot could also involve a miscommunication or misunderstanding. Ginny might think that Harry has some obligation to marry her, like a promise he made unknowingly in the past. So she takes it upon herself to make sure he fulfills this 'promise'. And Harry, being the good - hearted person he is, may initially resist but then start to see things from Ginny's perspective due to some events in the fanfic.
Harry would probably become more reserved and distant from Ginny at first. As the story progresses, he might try to find a way to break free from the forced marriage situation. Ginny would have to grow as a character too. She may realize the error of her ways and try to make amends. Their friends, like Ron and Hermione, would play important roles in either supporting or opposing the forced marriage, which would also shape the development of Harry and Ginny.
For Harry, he may face a lot of criticism from his friends and the wizarding community. They might see him as a heartbreaker or someone who doesn't value his relationships. This could lead to a strain on his friendships, especially with the Weasley family who he is very close to.
One possible plot could be that Harry plans a very elaborate and private proposal. He takes Ginny to their favorite place in Hogwarts, perhaps the Room of Requirement set up as a beautiful garden filled with the flowers Ginny loves. He gets down on one knee and tells her how she has been his rock through all the post - war chaos and how he can't imagine a future without her.
At first, their relationship might become strained. Harry, being forced into the marriage, could be cold and distant towards Ginny. However, as time passes, they might start to understand each other's situations better. For example, they could share their fears and frustrations about the forced union, which could gradually bring them closer.
It could be that they are on a mission together and get poisoned by some magical substance that has the side effect of making them drunk. In their inebriated state, they start reminiscing about their past, from their first meetings to their first kisses. This trip down memory lane makes them realize how much they truly love each other and how far they've come as a couple.
One possible plot could be that Harry is under the influence of a dark spell. In this state, he kidnaps Ginny because the spell is making him act against his true nature. Ginny, being the strong - willed character she is, tries to break through to Harry and reverse the spell's effect on him.
Typically, in a 'Harry forces Ginny fanfic', there's often a strong focus on the dynamic between Harry and Ginny. It might involve Harry taking a more assertive role in their relationship, perhaps in a situation where Ginny is initially resistant or hesitant.
One popular 'Harry forces Ginny fanfic' could be 'The Unexpected Bond'. It explores their relationship in a unique way, with some interesting plot twists that keep readers engaged.
One possible plot could be that they initially panic. Harry might worry about being able to protect his new family while Ginny would be thinking about how this would change their lives. They could face reactions from their friends and family, some being supportive and others expressing concern. Then they start to prepare for the baby, like finding a new place to live that's more suitable for a family.
In such a fanfic, perhaps Ginny has been feeling neglected by Harry due to his constant focus on fighting dark forces or some other important matters. So she starts to seek comfort in someone else. When Harry finds out, he first feels angry and betrayed. But then he realizes that he also had a part to play in their relationship going sour. He could then try to win Ginny back or decide to move on, depending on how the author wants to develop the story.