Well, first off, the characters are from completely different universes. Naruto has ninja powers and a very different cultural and story background compared to Sansa's medieval - like, political world in Game of Thrones. This makes it hard to create a believable and coherent story.
Another challenge is the so - called 'lemon' aspect. If it involves adult or inappropriate content, it goes against the rules of many fanfiction platforms. Even if it doesn't, writing such content in a tasteful way that still respects the characters is difficult. And combining it with two very different character types from different shows is an added complexity.
The character development would be a nightmare. Naruto is all about growth through training and friendship in a world full of ninja clans and battles. Sansa is about political survival and manipulation in a world of kings and queens. Merging their storylines and personalities while also adding the 'lemon' element (if that's what it implies) would require a great deal of creativity and probably a lot of stretching of the original character concepts.
The different character personalities pose a problem. Naruto is generally optimistic and energetic, while Sansa has been through a lot of trauma and is more complex. Combining them in a 'lemon' context while staying true to their characters is no easy feat. Also, the 'lemon' aspect means dealing with mature themes, which requires a certain level of writing skill to handle tastefully without making it seem out of place.
One challenge is the different universes they come from. Naruto has a ninja - based world with chakra, while Tohka is from a world with spirits and different power systems. Merging these two worlds in a believable way is difficult. Also, if it's a 'lemon' fanfiction, it might cross the line of appropriate content, which is a big no - no in many fan - fiction communities.
One challenge is character consistency. Vegeta is a proud Saiyan with a complex personality, and Android 18 has her own set of traits. Keeping them in - character while also developing a relationship between them can be difficult. For example, Vegeta is often focused on power and combat, so making his relationship with 18 believable requires careful handling.
Another challenge is blending the two different worlds. Naruto's ninja world with its jutsus and clans, and Inuyasha's feudal Japan - like world with demons and magic. Writers need to find a seamless way to bring these two together so that it makes sense for the story. It might involve creating new rules or concepts that bridge the gap between the two universes.
I'm not sure if there is a specific 'naruto and sansa lemon fanfiction' that is widely regarded as 'good'. Since Naruto and Sansa are from different fictional universes (Naruto from Naruto series and Sansa from Game of Thrones), a crossover like this in fanfiction can be quite rare and might not be of high quality overall. However, you could try searching on some large fanfiction platforms and read the reviews to see if there are any decent ones.
Well, first off, the 'lemon' part which implies mature content can be a big challenge as it may not be acceptable on most platforms. And writing a crossover also requires a good understanding of both the Kagome - related universe and the other universe it's being crossed with. You need to blend the characters and storylines in a believable way.
One challenge is making the two universes blend well. Naruto's world has ninjas, chakra, and different clans, while Misty is from a world full of Pokémon. You need to find a logical way to connect them.
Character development can also be difficult. Since the two series have very distinct character personalities, when bringing Naruto characters into the Shadowhunter world or vice versa, the writer has to ensure that they still stay true to their original selves while also adapting to the new environment. For instance, Naruto's upbeat and determined nature might clash with the more somber and duty - bound Shadowhunters at first.
Another problem is creating a believable plot. Since the two stories have different storylines and themes, coming up with a plot that can incorporate elements from both in a logical and interesting way is not easy. It has to be something that fans of both series can enjoy and not seem forced. For instance, if you want to have a battle in the fanfiction, you need to consider how the Divergent characters' skills and the Naruto characters' jutsu would interact.
The power systems are quite different too. Naruto has chakra - based powers and unique jutsu, while Berserk has a more traditional medieval combat style with some elements of magic. Writers need to figure out how to balance these power systems when they bring the two universes together in a fanfiction. Maybe a Naruto character's jutsu could be adapted to fit the more brutal world of Berserk, or vice versa, but it's not an easy task.