Communication might be a big problem. Keith is often more of a man of action and keeps his feelings to himself, while Allura is a princess used to expressing her thoughts and leading. They would need to learn to communicate better. For example, Keith might not understand why Allura is so insistent on certain diplomatic protocols during their marriage, and Allura might not get why Keith is so eager to jump into dangerous situations without discussing it with her first.
One challenge could be time management. They are both important figures in the fight against evil in the Voltron universe. So, finding time for each other between battles and diplomatic meetings would be tough. For instance, Keith might be called away on a dangerous mission right in the middle of their anniversary celebration.
One challenge could be cultural differences. Konoha and Suna have different traditions and ways of life. For example, the Hyuga clan has its own strict family rules which might conflict with Suna's more laid - back approach in some aspects. Another challenge is the distance between their villages. Maintaining a relationship while being so far apart for official duties can be tough. Also, their friends and families may have different expectations. Hinata's family might be worried about her moving to Suna, and Gaara's council in Suna may have concerns about a Konoha - native being so close to the Kazekage.
Another challenge could be Naruto's duties as a hero in his world. He might be called away often to deal with threats. This could leave Shion feeling lonely or neglected at times. She would have to be understanding of Naruto's responsibilities, and Naruto would have to find a way to balance his duties and his married life.
One challenge could be dealing with their different clan cultures. Naruto is from the Uzumaki clan and Hana from the Inuzuka clan. Their traditions regarding family, festivals, and even child - rearing might be different. Another challenge could be Naruto's dangerous missions. Hana would be constantly worried about his safety, and Naruto would have to balance his duties and his new family life.
One challenge could be acceptance from their respective villages. The Leaf village might be hesitant to fully accept Haku, given his past association with Zabuza. Similarly, the Hidden Mist might have reservations about Naruto, a Leaf ninja. Another challenge could be jealousy from other characters who might have had feelings for either Naruto or Haku. For example, some of Naruto's female friends in the Leaf village might not be happy about his marriage to Haku.
One challenge could be dealing with different family expectations. Shizuru's family might have certain traditions they expect her to follow in the marriage, while Natsuki's family could have different ideas. For example, Shizuru's family might want a large, elaborate wedding ceremony, while Natsuki's family prefers a more simple and private affair.
One challenge could be acceptance. Since Ichigo is from the human world and a Shinigami, and Nemu is an Arrancar, their union might not be easily accepted by either the Soul Society or the Arrancar community. Another challenge could be communication. They come from different backgrounds and cultures, so understanding each other's values and ways of thinking might be difficult at times.
Love and friendship is also a major theme. Some fanfictions focus on a romantic relationship between them, while others emphasize their strong friendship. In either case, their relationship is often at the center of the story, with elements of loyalty, sacrifice, and growth.
One common theme is the exploration of their cultural differences. Keith comes from a different background compared to Allura, and fanfictions often play around with how they bridge that gap. For example, in many stories, they teach each other about their respective cultures, which enriches their relationship.
In fanfiction, they might face the challenge of acceptance from their respective communities. Some in the Soul Society might think that Unohana is marrying beneath her status by choosing Ichigo, a human - turned - Soul - Reaper. In the human world, Ichigo's friends and family might have a hard time understanding his relationship with a Soul Reaper from a different dimension. Also, their different fighting styles and approaches to dealing with threats could cause friction in their relationship. For example, Ichigo is more impulsive while Unohana is more calculated. But through communication and compromise, they could overcome these challenges.
They might face challenges like cultural differences. Ranma comes from a more traditional martial arts family, while Ryoga has his own unique background. There could also be issues with their living arrangements. Ryoga is often lost, so he might have trouble getting home on time, which could cause arguments. And of course, their friends' reactions could be a challenge. Some friends might not accept their relationship easily.