Ghoul

A ghoul is an extremely violent being in the world of Tokyo Ghoul.

They feast on human flesh and have kagunes, large tentacles that usually come out of their back. Some ghouls even have kakujas which they can get from cannibalizing ghouls. (Eating other ghouls). This makes their RC cells go through the roof and they start displaying tremending power.

Ken Kaneki was the first Kakuja User we saw in the show. The reason he got a kakuja is because he ate Jason, who also ate ghouls (either that or he just had high rc cells) and gained all of HIS RC Cells. This triggered a reaction in Kanekis body and gave him his 'Centipede' Kakuja.

Ghouls are normally hunted by the CCG, an anti ghoul organization, who would kill ghouls, using their Quinques, which they would get from killing ghouls and turning a Kagune into a Quinque.

The members of the CCG are normally skilled and strong. (especially Furuta *wink* *wink* to all the :RE watchers)