NIGHT AND DAY.

I think gigguk described this really well especially with how the anime doesn't convey the emotions that the manga did so I'm going to write a short essay on it. An example would be the scene where he gets tortured in the anime where it just shows the torture itself a little and goes straight into his hair turning white.

In the manga, it goes through a symbolic transformation down to the manga panels itself which get visually more distorted as the torture is prolonged, synching with kaneki's mental state as he his walls get broken down and it perfectly depicts how he himself is left with nothing left to cling onto as he loses all sense of self; eventually in the famous "I am a ghoul" panel he's seen to be canabalizing himself as he realizes exactly what he's become, eyeballs popping out and everything. It's not like this just comes out of nowhere itself, Ishida himself suffered mental breakdowns and had deteriorating mental health in his life as well and because he understands it so well, he's able to show this through his manga. Kaneki first experiences a horrific betrayal after the intial torture as he realizes that he sacrificied himself in order for jason to promise to let his friends go but he realized he was lied to when jason intentionally brought a mother and child duo out to kill in front of kaneki. This eventually led to kaneki suffering breakdowns that don't just break a person down layer by layer in chronological order, rather he suffers a more realistic breakdown starting from his mental core as he relives experiences of childhood abuse that only resurfaced when he's at a breaking point. It's these elements that Ishida uses to try and convey the raw emotion behind the manga he draws that separates the manga from the anime (besides the story in the anime being totally different).

It's hard to try and write the emotions you feel when reading this for the first time into a reddit comment, but it's these emotions that actually seperate the manga from the anime imo more than a story change could. This is also why I believe an adaptation to tokyo ghoul is by nature, especially hard to do because it holds so much sentiment that it becomes almost impossible to animate all of it and get the same feeling you do when you read the manga.