Well, it's not easy to say off the top of my head. Different manga series might number their chapters differently for the Shibuya Arc. You could try searching on manga-specific websites or asking in manga communities for the accurate chapter.
I'm not entirely sure as it could be a specific visual novel related to Shibuya. It might involve stories set in Shibuya, with characters experiencing various adventures, romances or mysteries in that location.
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.