Another plot could be a crossover fanfiction. Imagine Kenichi meeting characters from other martial arts - themed anime. He could engage in friendly sparring matches or learn new techniques from them. This would not only expand his skills but also create interesting interactions between different anime universes.
One idea could be exploring Kenichi's further training in different martial arts styles from around the world. Another could be a 'what if' scenario where Kenichi has to face all his opponents at once. Maybe a fanfic about Kenichi teaching martial arts to a new generation of students.
A really interesting plot could be that Kenichi discovers a hidden mode in a popular fighting game that is actually based on real - life martial arts techniques. He starts to study the game to learn new moves and then has to face off against other players who also discovered the mode and are misusing the knowledge for evil purposes in the game world.
One interesting plot twist could be when Kenichi discovers that the game world he's been playing in is actually a training ground set up by his master in the real world to test his limits. Another might be that a character he thought was an ally in the game is actually a spy from a rival martial arts school trying to steal his techniques.
There might be a fanfiction where the worlds of 'Naruto' and 'Kenichi: The Mightiest Disciple' collide. Maybe the villains from both universes team up, forcing Naruto and Kenichi to form an alliance. They would have to overcome their differences in combat styles and strategies to defeat the combined evil forces.
Well, it could be about an original character (OC) who joins the world of 'Kenichi: The Mightiest Disciple'. The OC might be a new student at the dojo. As for the harem aspect, perhaps the OC has unique qualities that attract multiple characters from the series, like Miu or Shigure. They might start to develop feelings for the OC, leading to various comical and romantic situations as the OC tries to balance training and these new relationships.
A simple plot could be that Kenichi is transported to the Naruto universe. He is confused at first but then realizes he can learn a lot from the ninjas there. He starts training with Naruto and learns how to use chakra. In return, he teaches Naruto some of his self - defense moves.
One possible fanfic could be about a crossover where Naruto and Kenichi meet. Maybe Naruto visits the world of Kenichi and they end up training together. Naruto could teach Kenichi some of his ninja techniques, while Kenichi shows Naruto his martial arts skills.
One interesting aspect is seeing how Kenichi's martial arts skills interact with the powers and abilities of characters from other universes. For example, if he crosses over with a superhero universe, how would his punches and kicks compare to super strength or laser vision? It creates a lot of potential for exciting battles and power comparisons.
The masters of Ryozanpaku are very interesting to write about. For example, Akisame Koetsuji. You could write a fanfiction where he takes on a special mission outside of the dojo, using his unique martial arts skills. Or a story where he trains a new student with a completely different personality from Kenichi, showing his adaptability as a teacher.
Miu Furinji is also a great character. She is a strong martial artist and has a mysterious past. Her relationship with Kenichi, which is part friendship and part something more, adds depth to the story.