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.
It's fictional. The story was crafted by the writer to entertain and engage readers rather than being based on real events. Many elements in it are imaginative and not drawn from actual happenings.
Family relationships are also a key theme. There are complex family dynamics that play out throughout the story, like the relationship between the main character and her parents. It shows how family can both support and constrain an individual in different ways. For example, her parents' values and actions influence her own journey of growth.
Another important character could be some of Ellen's friends or acquaintances she meets during her adventures in the wide world. These characters help to further develop the plot and Ellen's understanding of the world around her. For example, a friend might introduce her to new ideas or ways of life that she hadn't considered before.