Perhaps the marriage law is part of a new wizarding world order to promote unity between different factions. Snape, being from Slytherin and Harry from Gryffindor, their union is seen as a symbol. They might face a lot of opposition from various groups. Some of Snape's old Death Eater associates might try to undermine the relationship, while some of Harry's friends might be very skeptical. However, through facing these challenges together, they gradually develop a bond that surprises everyone, including themselves.
The plot could start with Snape and Harry trying to find a way to get out of this marriage law situation. They search for loopholes in the law, all while being forced to participate in pre - marriage counseling sessions in the wizarding world. During these sessions, they are forced to talk about their past grievances and secrets. This leads to some explosive arguments at first, but eventually, it helps them to clear the air. As they dig deeper into each other's pasts, they find that they have more in common than they thought, and this could be the start of a relationship that neither of them expected.
One possible plotline could be Snape finding drunk Harry in the Hogwarts corridors. Snape, being the strict teacher, might initially be angry but then realizes Harry is in a vulnerable state. He could take Harry to his office to sober him up and in the process, they have a conversation that reveals some hidden feelings or understanding between them.
A plotline might involve a dark magic situation where Snape has been cursed and Harry, as his donor, is the only hope to break the curse. As Harry gets involved, he uncovers secrets about Snape's past that change his perception of him. Meanwhile, Snape has to deal with his pride and accept help from someone he has long disliked, leading to a complex emotional journey for both characters.
Perhaps Snape, in a moment of weakness or out of some deep - seated sense of responsibility, decides to protect Harry in an extreme way. He treats Harry like a pet in that he provides for all of Harry's needs but also restricts his freedom. This could lead to a lot of internal conflict for Harry, who is used to being independent. Meanwhile, Snape has to deal with the other characters in the wizarding world who might not understand his motives for treating Harry this way.
Well, there could be a plotline where Snape's father was an inventor in the wizarding world. He might have created some powerful magic items or spells that were lost or forgotten. Snape, in the fanfiction, could be on a quest to find and revive his father's work. Another idea is that Snape's father was a key figure in a war long before Voldemort's rise, and his actions had consequences that Snape has to deal with in the present day of the fanfiction. There could also be a plotline where Snape's father was a mentor to some other important character, and this connection has implications for Snape's life and the overall story.
One possible plotline could be that it's the result of some dark magic gone wrong. Maybe a spell was cast on Harry by an enemy of Snape's to embarrass him, and now they have to deal with the consequences together. Another could be that it's part of a prophecy that no one expected, and they must figure out how it fits into the wizarding world's future.
One possible plotline could be Harry being sold due to some dark magic plot against him. Snape then has to deal with this unexpected situation and protect Harry from further harm. Another could be that it's a part of a deal to save the wizarding world, and Snape and Harry must learn to work together in this strange new dynamic.
Another plotline could be that there is a spell or a magical occurrence that forces Snape and Harry to be close to each other. Initially resistant, Snape eventually gives in and cuddles Harry. This could then be the start of a journey where they learn to trust and rely on each other more.
Well, one possible plotline could be that Snape is examining Harry for some sort of magical ability or deficiency that he suspects. Maybe he's trying to figure out why Harry has such an affinity for certain spells. Another could be that Snape is examining Harry as part of a school investigation, perhaps related to some mischief that's been going on. And it could also be that Snape is secretly examining Harry to protect him from some hidden danger in the wizarding world.
Well, a plot could be that Snape adopts Harry due to some unforeseen circumstances. For example, Dumbledore in his infinite wisdom decides that Snape is the best person to protect Harry. Snape initially hates the idea but as he spends time with Harry, he starts to see Lily in him, not just in appearance but in his kind heart. This makes Snape more protective. Harry, for his part, is initially scared of Snape but soon realizes that Snape is actually trying to help him grow into a powerful wizard. They start to have a mutual understanding, and Snape helps Harry with his studies and also with dealing with the trauma of his past.
One possible plotline could be that Snape initially resists having Harry as an apprentice because of his hatred for James Potter. But as he gets to know Harry, he realizes that Harry is his own person. He then begins to teach Harry some of his unique potions skills and secrets about the wizarding world that Dumbledore may not have shared. Harry, in turn, helps Snape see the good in the students he has always been so harsh on.