Ghoul

Ghouls (喰種, gūru, translates to eater species) are a carnivorous species that is only able to feed on humans and other ghouls. They are as close to humans as possible: They normally have the same appearance as a human. If certain rare conditions are met, ghouls and humans may even be able to have offspring (see One-Eyed Ghoul), and a ghoul's organs can be successfully transplanted into a human.

Due to their feeding habits, ghouls are prosecuted by CCG.

Feeding Habits
Besides water and coffee, a ghoul can only feed on humans and ghouls. They are unable to digest any other type of food due to a particular enzyme their bodies produce. The structure of their tongues are also different from humans', making other foods taste disgusting and uncomfortable.

While ghouls can't eat normal food, they can drink coffee for some unknown reason. They are also able to drink plain water.

If ghouls try to eat other kinds of food, they will be struck by a powerful urge to vomit. If ghouls are forced or force themselves to digest such food, it will degrade their physical condition.

Ghouls don't need to eat in the short term like humans do. They can survive for one or two months just feeding one body. However, some ghouls eat more simply for pleasure.

When a ghoul enters an extreme state of hunger, a ghoul will suffer extremely painful headaches. The ghoul will lose all his reason and will be driven by instinct alone. He will feed on anything to end this state, even on close friends. Touka Kirishima describes this state of near-starvation as hell.

Physical Characteristics
A ghoul has high physical capability. A ghoul is much stronger than an average human: He is able to send an average human flying if he hits him strong enough and the ghoul can penetrate a human's body with his bare hands. Ghouls are also able to jump several meters high.

Under normal conditions, ghouls have a high regenerative ability: Small wounds and fractures heal in a matter of hours to a day, and even grave wounds heal after few days, as long as a ghoul has adequate food supply.

Ghouls have better senses than humans. They can smell people or meat from afar and can tell apart humans and ghouls by their smell. They also have a heightened sense of hearing that even allows some ghouls to discern individual footsteps from far away.

Ghouls seem to age like humans.

Biology
Ghouls have a "Rc factor" ten times higher than a human.. If the average healthy human has about 200-500 Rc level, then the ghoul has about 1000-8000 Rc level.

Ghouls have a main weapon that is described as their claws, called Kagune. It can be like a sharp wing or simple claws or even a tail, depending on the ghoul's materials and his own Rc type. Another "monstrous" trace is the Kakugan, what is called for ghoul's red eyes. Ghouls can turn their eyes red by their own will or maybe also by lusting food and using their "monstrous" powers.

Those "monstrous" traces in ghouls have unknown origin. Humans have got classified in biology taxonomy but ghouls have not, and that increases the mystery about ghouls.

Lifestyle
Ghouls can pretend to eat food in order to fool other people into believing they are human. They have to make themselves throw up soon afterwards, or they'll become sick.

Variants

 * A One-Eyed Ghoul is a human-ghoul-hybrid.