Perhaps there are other characters in the story like fellow disciples or antagonists. Fellow disciples could bring in elements of competition or camaraderie. Antagonists, on the other hand, would create conflict and obstacles for the main character, the disciple, which in turn would make the story more exciting.
The disciple himself is likely to be an interesting character. His journey from being a novice to someone who is more knowledgeable and capable is always engaging to follow.
One of the main themes could be the growth of the disciple. As the story progresses, the disciple might face various challenges that force him to learn and evolve.
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.
The grandchild is likely one of the main characters. Since the title mentions the wise man's grandchild, he or she is probably central to the story.
The main character is Shin, who is the grandchild of the wise man. There are also his friends and comrades in the story, like Sizilien and others.
Saitama is definitely one of the most interesting. His simple life goals like just being a hero for fun and his overpowered nature make him unique. Genos is also interesting. His quest to become stronger and his loyalty to Saitama create an interesting dynamic. King, too, is a great character. He's seen as a very powerful hero but in reality, he's just an ordinary guy who gets lucky and has to keep up the facade." "Answer2": "In the One Punch Man light novel, Saitama is the standout. He's so strong that he's bored most of the time because no one can really challenge him. Mumen Rider is also quite interesting. He's a low - level hero but has a huge heart and strong sense of justice. He's always trying his best even when facing opponents way out of his league. And then there's Tatsumaki, the powerful esper. Her short - tempered and somewhat bratty personality makes her an engaging character." "Answer3": "Well, Saitama is the most obvious choice as he is the protagonist and his one - punch - kills are just amazing. But also Sonic is really interesting. He's a ninja who constantly challenges Saitama and has his own set of skills and a rather cocky attitude. Another character is Fubuki. She's a powerful psychic and has her own group of followers. She's always trying to prove herself and often has a bit of a rivalry with Tatsumaki, which makes her character very engaging.
Kenichi himself is very interesting. His transformation from a bullied weak boy to a strong martial artist is quite engaging. Then there's Miu, she is not only a strong fighter but also has a complex personality.
There are the four wise men, of course. Each of them has their own characteristics. And there might be other characters that they meet during their journeys, like the people in the villages they pass through or the ones who offer them shelter or advice along the way.
There are the fourth wise man himself, and presumably there were other people he met along his journey like the sick, the poor, and the oppressed. And of course, the other three wise men are also part of the story's context.
The main characters are, as the title suggests, the foolish man and the wise man.
Denji is definitely one of the most interesting. His simple desires like wanting to touch boobs at the start make him seem very relatable in a crude way, but as the story progresses, his complexity emerges as he grapples with his new powers and responsibilities.