You can use free editing software available online. Some popular ones include OpenOffice Writer or Google Docs. They offer basic editing tools without any cost.
One great option is Google Docs. It's free, cloud - based, so you can access your work from anywhere. It has basic formatting tools for writing and editing, and it's easy to share with others for feedback. Another is LibreOffice Writer, which offers a wide range of features similar to paid word processing software. It allows for detailed formatting, spell checking, and has a large number of templates. Also, yWriter is a good choice specifically designed for novel writing. It helps you organize your chapters, characters, and plotlines easily.
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.