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.
In New World episode 12, Xu Tian suspected that Jin Hai had killed Little Duo and decided to lay his cards on the table. He told his father and Guan Baohui about his suspicions and requested that Jin Hai be sent to the police station. Guan Baohui went back to her parents 'home to complain to Xu Tian. She thought that Xu Tian and Jin Hai looked down on women. After Xu Tian and Guan Baohui argued, he began to wonder what he would do if Jin Hai really killed Little Duo. He asked his father, but his father thought it was impossible. However, San Er confirmed the fact that Auntie Liu saw blood on Jin Hai's hands that night. Xu Tian decided to let San Er tell Jin Hai to go to the police station after he came back. He could not refuse. Mr. Xu forced Guan Baohui to go to the police station to find Tie Lin. The matter was about to blow up.
It's hard to pinpoint exactly where Gojo is at any given time in the manga. His whereabouts change as the story progresses and different scenarios unfold. It could be in a supernatural realm, a mission site, or interacting with other characters.