Perhaps in a fanfiction, Harry is on a journey to find a sense of normalcy after all the chaos. Luna, being as unique as she is, shows him a different way of looking at life. They bond over their experiences with the Cursed Vaults and the fight against Voldemort. Eventually, they decide to get married and their wedding is a blend of both their personalities - full of strange creatures as decorations and the most delicious, magical food.
The plot might start with the announcement of the marriage law which forces Harry and Luna into a situation. Then they gradually get to know each other better in a new way. Luna's unique view of the wizarding world might influence Harry a great deal. They could also be involved in some sort of mystery related to the marriage law, like uncovering some hidden clauses or a conspiracy behind it. Their relationship would grow stronger as they face these things together.
A prevalent theme is the power of the contract itself. It can be seen as a magical force that brings them together, whether it's for good or for some initial chaos. For example, in many fanfictions, the contract might have some unforeseen magical properties that force Harry and Luna to interact more than they would have otherwise. Also, the theme of acceptance is big. They have to accept not only the contract but also each other's quirks and differences. Luna's unique view of the world and Harry's more traditional hero role need to be reconciled in these stories.
One common theme is the struggle against an imposed system. The marriage law forces them together, and they often have to figure out how to deal with their own feelings and desires while conforming to this new rule. Another theme is the discovery of new sides of each other. Since they might not have been that close before, they get to know different aspects of their personalities.
One popular 'Luna x Harry Marriage Law Fanfiction' is 'A New Beginning'. It explores how Luna and Harry navigate the challenges of a magically - enforced marriage law. The story beautifully portrays their individual personalities as they come to terms with their new relationship.
They would likely support each other's quirks. Harry would be understanding of Luna's dreamy nature and Luna would be there for Harry when his PTSD from the war flares up. Their relationship could grow deeper as they explore new magical things together, like traveling to far - off magical lands.
I really like 'Harry and Luna's Contractual Adventure'. In this fanfiction, the marriage contract is not just a plot device but a means to explore the deeper connection between the two characters. The author does a great job of writing their interactions, from the awkward moments at the start when they first learn about the contract to the heart - warming scenes where they support each other through tough times. There's also a lot of world - building within the story that makes it even more immersive.
For Harry, his growth could be shown through how he becomes more open - minded. He starts to embrace Luna's quirks and her different way of seeing things, which in turn makes him more accepting in general. For example, he might initially be a bit hesitant about Luna's belief in some of the more out - there magical creatures, but as they date, he starts to see the beauty in her imagination.
In a lot of fanfiction, they are indeed considered soul mates. Harry has been through so much trauma and Luna, with her off - beat charm and deep understanding, can reach parts of Harry that others might not. For example, she can see thestrals because she has also witnessed death, which gives them a special connection that some writers like to explore as a soul - mate - like bond.