There could be a samurai who is loyal to his lord. He might be a key character, facing moral dilemmas and challenges in the complex world of the shogunate. Also, there might be a foreign character who brings a different perspective to the story, interacting with the Japanese characters and learning about their culture.
One of the main characters is likely to be a powerful shogun or a daimyo. They are at the center of the political and military power.
In 'shogun the novel', perhaps there is a shrewd and powerful female character who has influence in the court, despite the male - dominated society. And there could be an old, wise advisor to the shogun, whose counsel is highly valued. There may also be a young and ambitious samurai on a quest for honor and recognition within the complex web of the shogunate's power structure.
Lady Mariko is also a significant character. She is caught between two cultures, being Japanese but having to interact closely with Blackthorne. She is intelligent and plays a crucial role in many of the power plays and cultural exchanges that occur. And there's also Yabu, a daimyo who is involved in the political and military struggles in the story.
In the 'shogun novel', main characters often include the shogun himself, who wields great power and influence. There may be a foreigner, perhaps a trader or an adventurer, who gets caught up in the complex web of Japanese politics. And of course, there will be samurai characters, some of whom are key players in the power struggles and battles that take place in the story.
There could be a young and ambitious samurai as one of the main characters in the 'shogun story'. He might be on a quest to prove himself in the eyes of the shogun. And there could be an old and wise advisor to the shogun who plays a crucial role in the story, guiding the shogun's decisions and actions. Also, a mysterious stranger who enters the shogun's territory and disrupts the existing order could be another main character.
The Raiden Shogun herself is surely one of the main characters. Her presence is central to the story as it's about her. Another could be her retainers, like Yae Miko, who has a significant relationship with the Raiden Shogun and might play an important role in the events of the novel.
Again, without more details about the 'shogun original story', it's hard to say. But likely there would be shoguns themselves as main characters, and perhaps some of their loyal samurai or advisors.
Most likely, the main characters would be the shoguns themselves. For instance, Tokugawa Ieyasu would be a key figure if the story covers the Tokugawa shogunate. There might also be important samurai who served under the shoguns, like Honda Tadakatsu.
Since I don't know the exact 'Shogun Love Story', I can't say for sure. But it's likely to have a shogun as one of the main characters. There might also be a love interest, perhaps a court lady or a commoner.
Since I don't know the exact story, it could be the shogun himself as the main character. There might also be his loyal samurai warriors who served him.
Obviously Naruto is one of the main characters since it's in the title. There might also be other Naruto -verse characters like Sasuke or Sakura who could be part of Naruto's entourage or have their own roles in this Western - inspired setting. And perhaps there are new characters created specifically for this fanfiction, like local lords or samurai who interact with Naruto.
Since it's a Naruto - related fanfiction, Naruto is bound to be a central figure. However, the story might also focus on some original characters created for this particular fanfic. These could be characters who are part of the shogunate court, such as samurai who serve under Naruto or members of the nobility who interact with him. And don't forget his ninja comrades from Konoha. They may come to visit Naruto in his new role, and their relationships and interactions could be an important part of the story.