Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
I don't know who the author of the 'one hand clapping novel' is. There are so many novels out there and without more information it's difficult to determine the author.
Well, without more context it's hard to say precisely. However, it could be a work of fiction that plays with the idea of the unexpected. One - hand clapping defies the norm, so perhaps the novel is filled with plot twists and turns that break the traditional narrative structure. It might also explore themes of solitude and the power of the individual, as one - hand clapping is an act that one does alone, yet can have profound implications.
I'm not entirely sure as I haven't read it specifically. But generally, it might explore some deep philosophical or psychological concepts, perhaps related to the idea of achieving something seemingly impossible like the sound of one hand clapping, which could be a metaphor for self - discovery or enlightenment.