The Washuu clan (和修家, Washū-ke) are a ghoul clan that originated from the Middle East. They have frequently practiced cannibalism throughout their long history, giving them powerful RC cells even from birth. They were involved in the formation of the CCG and are the central family leading it. Its members have hunted ghouls for well over a century, exterminating them using specialized methods. In 1890, the Japanese government enlisted the family in the founding of the Counter Ghoul Institution (喰種対策院, Gūru Taisaku in), a federal government agency that would manage and pursue ghouls. Since then, its members have acted as prominent officials within the law enforcement agency.
It is noted that Washuu members are known for being serious investigators who are concerned about results and are hard to get along with, as they are willing to sacrifice many people to complete their missions, perceiving fellow investigators only as numbers. The only known exception is Yoshitoki Washuu, who is notable for having been hospitable and benevolent to his subordinates.
Eto Yoshimura later claimed the Washuu clan has a long-standing alliance with the ghoul organization V. She further alleges that the clan was involved in a conflict with a powerful one-eyed ghoul and this conflict resulted in the formation of the CCG.
Ironically, the Washuu clan is actually comprised of ghouls posing as humans. Using their authority, they have kept their true nature secret since the formation of the anti-ghoul law enforcement agency they administrate. Itsuki Marude discovered their secret through a personal investigation of the family's members. He explains that he found absolutely nothing suspicious except for one minor detail: when he examined the records for the Rc Scan Gates, he noted they registered a false positive whenever a Washuu walked through them.
It is later revealed by Kaiko that the Washuu Clan used V as corpse collectors, and the Washuu ate the corpses of dead investigators in order to replenish their need for human meat.
Having practiced cannibalism for centuries, the Washuu Clan are considered to be "natural-born Kakujas." While other ghouls may develop a mutation in their Rc cells as a result of cannibalism, the Washuu bloodline carries a genetic mutation that causes these cells to naturally develop. Dr. Akihiro Kanou chose to focus on members of the Washuu bloodline in his experiments in order to take advantage of this enormously powerful bloodline.
So far, only the One-eyed ghouls created from Rize Kamishiro have demonstrated the abilities typical of a Kakuja. It is unknown why the members of the Washuu Clan have not displayed a kagune or any of the abilities associated with their unique bloodline.
The Washuu clan includes numerous branch families, tasked with carrying out different duties. At the head of these groups is the main family line, responsible for leading the CCG and being the public face of the larger clan. In secret, they also assign individuals to specific roles within a breeding program meant to preserve the pure-blooded lineage or to produce half-human agents to serve them. These individuals are known as "Seeds" and "Wombs," responsible for siring or bearing offspring to further the clan's agendas. According to Souta Washuu-Furuta, these breeding programs involve incestuous and non-consensual relations between the primary Washuu bloodline and "Wombs."
- Daikichi Washuu † - CCG Founder
- Yoshiu Washuu † - Chairman
- Tsuneyoshi Washuu † - Chairman
- Yoshitoki Washuu † - Bureau Director
- Matsuri Washuu - Special Class Investigator (Formerly)
- Iyo Washuu (Formerly, Divorced)
- Kishou Arima †  - Special Class Investigator
- Yusa Arima - Peacekeeper
- Kishou Arima's mother - Womb
- Kichimura Washuu † (Nimura Furuta) - Rank 1 Investigator / Former Bureau Director (Resigned from the CCG)
- Kichimura Washuu's mother - Womb
- Hairu Ihei † - First Class Investigator
- Shio Ihei †  - Ghoul Investigator (Formerly)
- Suzu Sanzu - Peacekeeper
- Kaiko †
Unknown other families
- Rize Kamishiro † - Womb (Formerly)
- Rize Kamishiro's mother - Womb
- Half-human agents from the Sunlit Garden
- Underground King (Formerly)
- 2 unnamed members of Arima Squad
- When they become CCG leaders, the males of the Washuu Clan Main Branch add '吉' to their given names, meaning "good luck" :
- Tsune '常' became Tsuneyoshi '常吉' ;
- Chika '時' became Yoshitoki '吉時' ;
- Nimura ' 二福' became Kichimura '吉福'.
- After slaughtering the majority of the clan Furuta dubs himself the Washuu King.
- Matsuri, the lone survivor of the Washuu family is revealed in the epilogue to have vowed never to have kids, thus putting an end to the clan's longstanding history when he dies.
- Ken Kaneki, Nashiro Yasuhisa, Kurona Yasuhisa, the Oggai Squads and all experiments created by Akihiro Kanou utilizing Rize Kamishiro's kakuhou all contain the Washuu clan's unique Rc cells and thus may display certain distinctive genetic traits of the bloodline. This is noted by Dr. Kanou to be the reason Ken Kaneki's Dragon Kakuja so eerily resembles the form taken by The Underground King's Naaga.