Well, first you need to have a clear storyline in mind. Think about the characters, their personalities, and the conflicts they might face. Then, start sketching out the frames and poses of the horses and their interactions.
Love and friendship are common themes. In many lesbian anime stories, the characters start as friends and then realize their deeper feelings for each other. For example, in 'Sakura Trick', the main characters' friendship evolves into a romantic relationship.
No, it's not appropriate. Anime fanfiction should generally promote positive values. The ideas of kidnapping and bondage in a lesbian context are not only against the principles of respect and consent but can also make some readers uncomfortable. The anime world has so many great themes like friendship, adventure, and self - discovery that are much more worthy of exploration in fanfiction.