Kagune

A Kagune (赫子, shining child) is a ghoul's predatory organ and functions as their weapon and claws. It is usually as red as blood (the colours are varied in the anime to distinguish the kagune of each individual); and flexible like the flow of water (Also called liquid muscle.), but firm and sturdy. When released, a ghoul's physique is strengthened, they are more resilient and their mobility heightens. A kagune is composed of Rc cells, which flow just like blood, can become as solid as teeth and can be described as "liquid muscles". The Rc cells are released from a kakuhou piercing the skin, and the released Rc cells form the kagune. A kagune can be repeatedly hardened and softened at will by the ghoul.

Although a ghoul's healing ability is high, the healing of wounds tends to be delayed if the wounds are inflicted by a kagune. It is also evident that in order to counter a kagune in battle, one must also have a kagune, if not, at least something in relation to a kagune. Hence, Ghoul Investigators use kagune-based quinque as a tactical means to battle against ghouls. Also it seems that the kagune are voluntary muscles as ghouls can control them whenever they want.

Rc Types
The kagune's appearance and the place of emergence on the body depend on the Rc type of the Ghoul.

There are four different Rc types: Ukaku, Koukaku, Rinkaku and Bikaku. As a guideline, each type can characteristically subdue another type, although it may be different for two specific opponents.

Each Rc type has a set of strengths and weaknesses, each one unique to it's type. These are exploited by CCG in the creation of the Quinque and Q bullets.

It is also possible for a child to inherit separate kagunes from each parent to express distinctive hybrid traits as shown with Hinami Fueguchi and the Nutcracker.

Ukaku
An Ukaku kagune (Japanese 羽赫, romanization ukaku, English approximately shining feather) is spread out like feathers and is released from the shoulder area, it specializes in high speed attacks, most of the users seeming to have hugely enhanced speed. The kagune is lightweight and can be used to deliver high-speed attacks against an adversary, the primary method of attack is crystallising their kagune to deliver a high speed torrent of spike like projectiles, however whilst crystallised they are much stiffer and can't be used for short range combat. While the kagune is suited both for short-distance and long-distance attacks, although short-range is considered their weakness. They are able to use their kagune as a shield and some users are shown to be able to shape them into sharp blades, reminiscent of a Koukaku, to aid in close quarters.

Altogether, ukaku-type ghouls have a high chance to end the battle after a short time.

However, releasing the Rc cells extremely decreases stamina. Thus, ukaku-type users lack endurance and are at a disadvantage if the battle drags on for a long time.

Ukaku kagune can use their speed and mobility to shoot down a Bikaku-type user. However, a koukaku-type user can surprise an ukaku-type user by successfully guarding against the ukaku-type user's attacks, leaving the Ukaku vulnerable to counterattacks and exhausting the ukaku-type user in the long run.

Known Ukaku Ghouls are Touka Kirishima, Yoshimura, Eto, Renji Yomo, Kaya Irimi, Ayato Kirishima, Kazuichi Banjou, Katou Sumihara, Hikari Kirishima, Ginshi Shirazu, and Seidou Takizawa.

Koukaku
A Koukaku kagune (Japanese 甲赫, romanization kōkaku, English approximately shining shell) is released below the shoulder blade. This is achieved by a high density of Rc cells. It is heavy and extremely robust. Of all the kagunes, they have the greatest sturdiness and are especially suited for defense. Normally, they are generally shaped into armors or shields. But on the offense, they can be shaped like melee weapons such as drills, hammers, blades, and swords.

Due to its high weight, a koukaku's speed is inferior to all other kagunes and the kagune is hard to wield.

A koukaku can fend off an ukaku onslaught using its guarding capabilities. However, a rinkaku kagune can deliver severe strikes against the slow koukaku, breaking their kagune and breaching their defenses.

Known Koukaku users are Shuu Tsukiyama, Ryouko Fueguchi, Hinami Fueguchi, Arata Kirishima, Naki, Minami Uruka, Kuki Urie, and Nutcracker.

Rinkaku
A Rinkaku kagune (Japanese 鱗赫, romanization rinkaku, English approximately shining scales) has an appearance similar to scaled tentacles and is released at the back around the waist. A rinkaku wielder has powerful regenerative abilities that some of them could even survive the most critical damage done to them. Kaneki Ken, a rinkaku, has abnormal regenerative abilities as he inherited Rize's kagune which is special because of its abnormal regenerating factor even among the rinkaku types. Its peculiar appearance and structure yield a superior striking power. A rinkaku excels in brute strength.

This type's regenerative power is a result of the Rc cells easily binding together. Their Rc cells are more similar to liquids. However, this means that the binding force among the Rc cells must be weak, therefore making the kagune very easy to break. But because their Rc cells bind so easily, some rinkaku can bind their multiple tentacle-like kagune together to make a larger, stronger kagune.

A rinkaku kagune can deliver severe strikes against the slow koukaku, penetrating the kagune and breaching the koukaku's defenses. However, a rinkaku has serious problems fighting against the balanced bikaku kagune: A bikaku has comprehensively high power, allowing them to fight against the brute-force rinkaku, and the rinkaku kagune's softness makes it comparatively easy for the bikaku to cut the kagune off. This disarms a rinkaku no matter how much strength it may possess, leaving the rinkaku at a disadvantage on the defensive. It has been shown that in some cases, a Bikaku's attack can disable a Rinkaku's regeneration.

Known Rinkaku Ghouls are Rize Kamishiro, Ken Kaneki, Nashiro Yasuhisa, Kurona Yasuhisa, Hinami Fueguchi, Asaki Fueguchi, Yamori, Nico, Kie Muramatsu, Saiko Yonebayashi, Karao Saeki, Roma Hoito, Kanae von Rosewald, and Matsumae.

Bikaku
A Bikaku kagune (Japanese 尾赫, romanization bikaku, English approximately shining tail) typically has a tail-like appearance and is released around the tail-bone/coccyx. It is good for medium-distance attacks and has decent offense, defense and speed. Thus, they have no notable strengths or weaknesses like the kagune based on other Rc types, meaning the kagune itself is treated as a surprise "trump card."

A bikaku has better speed and durability against the brute-force, breakable rinkaku, allowing them to cut off the rinkaku's kagune. However, a bikaku will be overwhelmed by the faster ukaku user and will lose against the ukaku's long-range attacks.

The balanced characteristics makes the kagune a preferred quinque type for investigators.

Known Bikaku Ghouls are Nishiki Nishio, the Bin Brothers, Enji Koma, Shachi, Tooru Mutsuki, Akashi Kobayashi, Nutcracker, Big Madam, and Miza.

Kakuja
When ghouls repeatedly cannibalize other ghouls, they rarely develop an abnormal kagune apart from the common predatory kagune. This kagune typically takes an armor-like shape, and ghouls with such a kagune are called kakujas.

This abnormal transformation kagune also takes after the Rc types.

Known Kakuja Ghouls are Ken Kaneki, Yoshimura, Eto, Yakumo Oomori, Arata Kirishima and Seidou Takizawa.