In Sui Ishida's Tokyo Ghoul, the world is divided into human civilization and the underworld of the Ghouls, who stalk human prey in the night. There's seemingly no room for a Half-Ghoul like Kaneki, who doesn't quite fit into either.
Kaneki became a Half-Ghoul when Rize Kamishiro's organs were transplanted into him, and he began to hunger for human flesh after developing a distinct red Ghoul eye. Kaneki felt like he had lost his humanity, but he couldn't stand the predatory, vicious ways of the Ghouls, either. He was stuck in the middle, searching for a place someone like him would be accepted.
Ken Kaneki Was Caught Between Two Worlds
Kaneki nearly lost his life when Rize, the "binge-eater," tried to eat him. Steel beams fell on and killed her, and Kaneki received her organs in a transplant operation by Dr. Kano. He awoke with no wounds or appetite and left the hospital with no distinct medical problems. But then he noticed that food tasted terrible, and he started to develop a new kind of hunger, one that threatened to tear his mind apart. Looking in the mirror, Kaneki saw that one of his eyes was completely blood-red -- a Ghoul's eye. Going crazy from all the changes, he needed answers and help fast. One night, while stumbling around, Ken found Touka just outside Anteiku the cafe and begged her for help.
Touka, disgusted by Ken's frightened and indecisive ways, turned him away as a supposedly inferior half-breed, though a certain Mr. Yoshimura of the Anteiku cafe welcomed him inside. He even offered Kaneki a package of guilt-free human meat and told him to visit again anytime. Impressed, but he not wanting to eat human meat under any circumstances, Ken instead struggled to find a solution himself. He realized that he could drink coffee, but it didn't help his hunger, which eventually caused him to run afoul of Nishiki Nishio, a Ghoul with territory near Ken's college. One night, Nishiki corners Kaneki and his friend Hide, nearly killing them both. That was when Touka stepped in, and this time, she would stay in Ken's life.
Anteiku Is Neutral Ground For Humans and Ghouls
Touka used her combat prowess to save Ken's life from Nishiki, and the injured and starving Kaneki collapsed. When he next awoke, he was in a nice room on Anteiku's second floor, being welcomed by Mr. Yoshimura. Turns out, this was no ordinary cafe; it was an established neutral zone of nonviolence, where Ghouls and humans could visit as patrons side by side. Hide was there too, despite being human, and would remain here until he recovered. Ken had found shelter at last, but he needed to make some adjustments.
Kaneki was accepted as an employee of Anteiku, and was given an eyepatch to cover his ghoul eye. He also had to undergo training to blend in better with human society; namely, pretending to eat human food. There was a trick to it, and Mr. Yoshimura taught him while educating Ken on all sorts of things to do with life as a Ghoul. Ken was still concerned that he didn't really belong anywhere, being only half-human and half-ghoul, but Mr. Yoshimura told him that he was a man of two worlds, not zero. Kaneki just had to take it slow, learn to brew a decent cup of coffee, and be nice to Anteiku's patrons. Ken was hesitant, but it was his best bet. And as he soon found it, Mr. Yoshimura was right... about everything.