Often, there are plotlines where they have to deal with misunderstandings between them. For instance, Arthur might misinterpret Shinra's actions, leading to a rift in their relationship that they then have to repair. There are also plotlines where they are pitted against a common enemy that forces them to work closely together and understand each other better, strengthening their bond.
Sure. One great place to start looking for shinra x arthur fanfiction is Archive of Our Own (AO3). There are numerous works there that explore different aspects of their relationship, from deep friendships to potential romantic undertones. Some fanfictions might focus on their adventures together in the context of the original story's world, while others could be more about how they support each other during difficult times.
Another theme is the exploration of their different personalities. Arthur is usually more responsible and DW can be more carefree. Fanfictions play with this by putting them in situations where their personalities clash at first but then they find a way to complement each other. For instance, in a story where they are planning a party for their parents, their different approaches initially cause problems but in the end lead to a great celebration.
Love and loyalty are very common themes. Celty and Shinra have a deep love for each other that is often the focus. Fanfics show how they are loyal to one another through various situations. Also, the theme of discovery is there. As Celty discovers more about the human world through Shinra, and Shinra discovers more about Celty's true self, these aspects are frequently written about in the fanfics.
A common theme is the exploration of their opposite personalities. Hibana is more reserved and Shinra is brash, so fics often play with how they interact with and complement each other.
Love and loyalty are often themes. Shinra is always very loyal to Celty, and their love story, which is quite unique given Celty's nature, is a central part. Also, the theme of discovery. Celty is constantly discovering more about the human world with Shinra by her side, and Shinra is learning about Celty's world as well.
A sense of loyalty is often a theme. In these fanfics, Shinra and Tamaki are shown to be loyal to each other. Whether it's facing external threats or internal doubts in their relationship, they stand by one another. And the theme of shared dreams can also be found, like they might have a common goal for the future.
One common plotline could be Arthur realizing his roughness is wrong and trying to redeem himself. Another might be Merlin getting fed up and leaving, which then makes Arthur see how much he needs Merlin.
One common plotline is Merlin using his age - related wisdom to save Arthur from various threats. For instance, he might have prior knowledge of a magical curse that's about to befall Arthur and uses his experience to counter it.
One common plotline is Merlin using his youth to his advantage. For example, he might be able to blend in more easily with the younger generation in the kingdom, gathering information that Arthur can't. Another is Arthur having to deal with his own insecurities about getting older while Merlin is full of energy. Also, there could be a plotline where Merlin's younger age makes him more adaptable to new magic or technologies that are emerging, and Arthur has to rely on him for that knowledge.
There are also fanfictions that focus on the emotional bond between them. It could be a deep, almost father - son like bond that is slowly eroded by events. Or it could be a more complex, codependent relationship where they both rely on each other in different ways for different reasons. And sometimes, the theme of redemption can come into play, especially if one of them has wronged the other and is trying to make amends.