How did Kaneki discover Touka was a ghoul? I've previously watched the anime and have just now started the manga (I know I'm terribly late) My mind is blown away by how different the manga is from the anime. (I'm even questioning if I'm reading the right thing due to the detail and differences) I feel like the question presented as my title will help resolve some of my suspicions. Did Studio Pierrot really cut so much detail out as well as change some parts of the story/events? Have I really been missing out on so much?

If someone could explain I'd deeply appreciate it

Thanks!
I've only watched the anime, but Kaneki discovered that Touka was a ghoul when he had just become a ghoul and entered Nishiki's territory. Touka had saved Kaneki from him.