For Pokemon Black and White fanfiction, you could write about a group of trainers who discover a hidden area in Unova that has never been explored before. In this area, there are ancient Pokemon and secrets about the origin of the region. The trainers have to work together to survive and unlock the mysteries. You could also write a story where a Pokemon gets lost from its trainer and has to find its way back through the various cities and routes of Unova. It could meet different Pokemon and humans along the way and have all kinds of adventures. Additionally, you could focus on the rivalry between two trainers who are both aiming for the top in the Unova Pokemon League and how their competition affects their growth as trainers.
One idea could be to explore the backstories of the Gym Leaders in more detail. For example, how did they become Gym Leaders? What challenges did they face on their journey? Another idea is to create an alternate universe where the roles of the heroes and villains are reversed. You could also focus on the relationships between the Pokemon and their trainers in a more in - depth way, like showing how they communicate and support each other outside of battles.
For a Pokemon Black and White fanfiction, you could write about a group of friends who all start their Pokemon journeys together. They each have different goals and Pokemon teams. As they progress, they face rivalries not only from other trainers but also from a mysterious new organization that is trying to disrupt the balance in the Unova region. This organization could be trying to control certain types of Pokemon for their own gain. The friends then have to work together, using their unique Pokemon skills and strategies, to stop this organization and protect the Unova region and its Pokemon. This type of story would allow for a lot of character development and exciting battles.
One idea could be exploring an alternate ending where the main villain has a change of heart before the final battle. Another could be a story centered around a new Pokemon species discovered in the Unova region post - game events. Maybe a fanfiction about a trainer who has to team up with a former rival to face a new, unexpected threat in Unova.
You could create a fanfic where the main character is a Pokemon Ranger working in Unova. Their mission could be to stop an illegal Pokemon trading ring that is stealing rare Pokemon from the wild. Along the way, they form bonds with different Pokemon and trainers, and they have to use their Ranger skills, like using the Capture Styler, to solve problems and catch the bad guys.
Another interesting concept is to write a fanfic from the perspective of a Pokemon in the Black and White world. For example, a Patrat that is part of a group trying to protect their territory from human encroachment. This would give a unique view into the Pokemon - human relationship and how Pokemon live in their natural habitats.
One idea could be to focus on a new trainer in the Unova region who discovers a rare and powerful Pokemon that no one has ever seen before. This Pokemon could have unique abilities that change the way battles are fought in the fanfiction.
One idea could be to explore the backstory of a minor character in the games. For example, the story of a Pokemon ranger who has a special connection with a rare Pokemon in the Unova region. Another could be to create an alternate universe where the roles of the heroes and villains are reversed. Maybe Team Plasma is actually the good guys trying to save Pokemon from some other hidden threat.
One idea could be that the main character discovers a hidden street in the Pokemon Black and White world that has a special name with a secret power. The power could be related to a unique type of Pokemon evolution. Another could be a story where the street name is the key to unlocking an ancient Pokemon mystery that has been forgotten over time.
One idea could be a story about a trainer who discovers a rare and powerful Pokemon in an unexpected place in the Unova region. This Pokemon has unique abilities that no one has ever seen before.
One interesting storyline could be an alternate version of Ash's journey in Unova. Maybe he starts with different Pokemon and has to face different challenges. For example, instead of Pikachu, he could start with a Tepig and have to deal with its over - eagerness to battle.
Some fanfictions focus on an OC's relationship with the main characters in Pokemon Black and White. For example, an OC could be a rival to the protagonist. Their rivalry could be more than just about winning battles. It could be about different ideals on how to treat Pokemon, with the OC having a more unorthodox approach that challenges the protagonist's views.