A one-eyed ghoul (隻眼の喰種 Sekigan no Gūru) is a human-ghoul-hybrid. Most ghouls treat their existence as an urban legend or have never heard of their existence at all.
Hybrids are labeled one-eyed ghouls because they only develop one kakugan, in contrast to normal ghouls who develop kakugans in both eyes.
Due to hybrid vigour, one-eyed ghouls are said to become much more powerful than normal ghouls.
Despite their hybrid nature, one-eyed ghouls can't digest human food, so they have to feed off humans and ghouls. Their food will be human or ghoul origin regardless so they are solely cannibalizing species.
Naturally-born hybrids are extremely rare. The chance of pregnancy is low, and even if the mother becomes pregnant, the child normally dies during pregnancy: If the mother is a human, the child will not get necessary nutrients and will starve to death. If the mother is a ghoul, the mother's body will mistake the child for food and reabsorb it. However, there are rumours that a naturally-born one-eyed ghoul exists.
The primary method of creating One-Eyed Ghouls is through transplanting a Kakuhou into a human recipient, an exceptionally high-risk procedure. In the rare event that the operation is successful, the human patient develops into an artificial hybrid with all the abilities of a normal Ghoul. This procedure was pioneered by Dr. Akihiro Kanou, with the first successful patient believed to be Ken Kaneki.
Quinx Squad Editar
After examining Dr. Kanou's surgery on Ken Kaneki/Haise Sasaki, the CCG created an experimental squad consisting of humans with ghoul capabilities through implementing a kakuhou covered by quinque steel layers. While the Quinx Squad's members aren't considered as normal half-ghouls due to their lower RC cell levels and the ability to eat human food still, they are made from the concepts of Dr. Kanou's half-ghoul experiments.
- According to rumours, there exists another one-eyed ghoul besides Ken Kaneki. Itori mentioned the witness reports were preposterous. This one-eyed ghoul seems to practice cannibalism due to his vigorous appetite. Uta advised Ken Kaneki not to search for him, because he never heard happy stories about the one-eyed ghoul. They were probably referring to Eto/One-Eyed Owl.
- Eto is the only confirmed case of a natural-born half-Ghoul.
- Fujishige Iba once mentioned to his subordinates that there was a scientist that wanted to experiment with hybridization, but his research was deemed unethical and shut down.