Shuu Tsukiyama.

Shuu Tsukiyama (月山 習, Tsukiyama Shū) is the infamous Gourmet (美食家, Bishokuka) ghoul of the 20th ward. He was a fourth-year student studying Social Welfare at the Department of Human Sciences at Seinan Gakuin University. He comes from the extremely wealthy and influential Tsukiyama family, headed by his father, Mirumo Tsukiyama. Tsukiyama himself became the head of his family after the Tsukiyama Family Extermination Operation. He was also a member of the Ghoul Restaurant, known as MM, until he betrayed them. He joined Kaneki's group with the hidden intention of eating Ken Kaneki, obsessed with his scent and taste, but eventually came to genuinely care for Kaneki. Two years later, his severe depression and anorexia after Kaneki's apparent demise left him emaciated and requiring constant care from his family servants. After finding out Kaneki was alive and meeting him, he recovers, being able to walk and eat on his own as well as take measures to help Kaneki regain his memories.

Tsukiyama is a tall, attractive young man with a gentle look likened to his mother's. He considers himself fashionable and usually dresses in European attire, though his sense of style is questionable. He typically wears formal suits or semi-formal dress shirts and long pants decorated with bold contrasting colors (usually red and purplish blue) and eccentric patterns such as stripes, flowers, or geometric shapes. His purple hair was usually neatly combed, with a characteristic long fringe neatly swept to the left. Upon his first appearance, Kaneki thought to himself that he looked like a model. He possesses a mask shaped like a crescent moon as a reference to his name.

Initially, Tsukiyama appeared to be a confident, friendly, and intelligent ghoul. However, these were merely acts to lure his "prey" into the Ghoul Restaurant and to conceal his eccentric, cruel, and selfish personality. He considered himself a strong predator who would seek to devour the finest meals he made of his "prey" and would not hesitate to resort to any merciless tactics in order to achieve his goals. As a result, he was disliked by most ghouls in the 20th ward. His interest in European literature and language was shown in his gestures and mannerisms, his dialogue often peppered with random phrases of English, French, and Italian. Family associates have likened his intellectual gestures to those of his young father.[4] (In the anime, he showed great anger towards others who disrespected his taste in food.) Tsukiyama felt insulted when Rize Kamishiro declined his invitation to join the Ghoul Restaurant, who mocked the "classy" eating habits of the restaurant that resembled the humans'. Therefore, Tsukiyama bore grudges against Rize and called her a "pig" for ridiculing his taste in food. He had poor control over his emotions, with intense outbursts or "meltdowns" especially when it came to losing something important or failing to capture his "gourmet target." During times when he was calm and rational, he seemed to be quite intelligent and often came up with strategies to help his comrades. He compared himself to a noble "knight," especially later when in the service of Kaneki. Besides food, he also enjoys reading, fashion, and playing the piano.

He is mentioned several times by members of the CCG as one of the main concerns for the CCG in the 20th ward, with the bulletin board outside the CCG 20th Ward's Branch Office requesting information, and is blamed by investigators for the loss of one of their men. After noticing the "lovely gradation" in Misono Karube's eyes, Tsukiyama stalked her at her home and stole them by gouging them out; he then had them sautéed. Tsukiyama later appeared at Anteiku, where he encountered Kaneki for the first time. After hearing about how Kaneki was able to confront the investigators—and noticing his enticing, unique scent—Tsukiyama took an interest in him. Aware of his unsavory reputation, Touka demanded that he leave. Though he complied, he promised Kaneki that they would meet again.

in the world there are two sides constantly confronting each other - ordinary people and ghouls. ghouls are the same people, a carnivorous and cannibalistic species, capable of feeding only on people or other ghouls. They are as similar to people as possible: as a rule, they have the same external appearance and the same developed intelligence, but their diet, mentality and internal structure are slightly different from humans. In rare cases, human and ghoul individuals are able to have offspring, and ghoul organs can be transplanted (with a low chance of success) into a human body. Because of their diet, ghouls are persecuted by the forces of nature CCG (organization for the killing of ghouls), deprived of any rights in human society, including the right to life. ghouls are able to feed only on human flesh or the flesh of other ghouls. The taste buds of ghouls are also different from humans, which is why the taste of ordinary food causes disgust and nausea in ghouls. If a ghoul tries to eat human food, it will subsequently experience a strong urge to vomit. Forcing itself to eat such food will result in the degradation of its physical condition. Ghouls, unlike humans, do not need to eat frequently. They are able to survive by eating only once every one or two months. However, some ghouls eat much more often for their own pleasure. Despite the fact that ghouls can go without human flesh for two months, some of them are able to eat up to eleven people at once in a short period of time. Such ghouls are also known as "devourers", one example of which was Rize Kamishiro. In addition, food is "fuel" for the use of ghouls' special abilities; frequent release of kagune and regeneration of wounds require more intensive nutrition. Ghouls have high physical abilities, which makes them much stronger than an ordinary person: by striking with sufficient force, they are able to throw a person into the air or pierce his body through and through.

In addition, the height of their jumps can reach several meters. Under normal conditions, ghouls have a high regenerative capacity. Minor wounds and fractures heal in a matter of hours; more serious wounds heal within a few days if the ghoul has a sufficient supply of food. Kagune (赫子, kagune) is a ghoul's hunting organ, used as a weapon. It is usually blood-red or black in color, flexible like a stream of water, but also hard and durable. After releasing the kagune, the ghoul's body is strengthened: it becomes more resilient, its movement speed increases, and its reactions become sharper. The kagune is made up of Rc cells, which circulate in the ghoul's body like blood. They are capable of acquiring a hardness similar to tooth enamel; in addition, they can be described as "liquid muscles". RC cells are released through the kakuhou located on the back, after which they form the kagune. After being released, the kagune takes on the state of a "controlled muscle", which the ghoul can either strengthen, making it stronger, or soften/relax. The size depends on the quality and quantity of Rc cells in the owner's body, while its shape is influenced by the ghoul's intelligence, creativity, and imagination. Kakuhō (赫包, kakuhō) is a sac-like organ that only ghouls possess. The kakuhō is designed to store RC cells. RC cells are recreated during the ghoul's feeding, after which they are transported along with the blood to the kakuhō, where they are subsequently accumulated. RC cells, piercing the skin, can be released through the kakuhō by the ghoul's will or during periods of intense excitement. Once manifested, they take the form of a kagune Kakugan (赫眼) is a ghoul's eye, with a red glowing pupil and black sclera. Often, red glowing "vessels" diverge from the kakugan's pupil, which are actually RC channels that.

One-Eyed Ghoul (隻眼の喰種, Sekigan no Gūru) is a human-ghoul hybrid that possesses the physiology of a ghoul. Most ghouls are either completely unaware of them or believe their existence to be an urban legend. Quinx (クインクス, kuinks) is a human with a quinque implanted in their body. Because the quinque resembles a kagune, quinxes can be mistaken for ghouls or half-ghouls. Quinke (クインケ, kuinke, labeled as "former enemy") is a weapon created from a ghoul's kagune. Made from a kakuhou, the quinque emits electrical impulses that stimulate the kakuhou, allowing control of the kagune. The Quinque can be created in various forms, such as bladed weapons/firearms or even armor, with most retaining some of the characteristics of the original Kagune. Another difference between the Quinque and the Kagune is that the Quinque can no longer evolve and absorb Rc cells.