|This is the article on the prison. For the movie, head to Naruto the Movie: Blood Prison.|
The Hōzuki Castle (鬼灯城, Hōzuki-jō, Literally meaning: Demon Lantern Castle), also known as the Blood Prison (ブラッド・プリズン, Buraddo Purizun), is a large castle in Kusagakure that serves as a criminal containment facility.
Prisoners interned at Hōzuki Castle are intended to remain there until they die or the hidden village that sent them there officially requests their release. There are several death traps spread throughout the fortress to prevent escape and, in Naruto the Movie: Blood Prison, the castle is situated on a cliff surrounded by whirlpools, drowning any who may try to swim away. Actual security within the prison is seemingly poor: despite all prisoners being subject to strip and body cavity searches, Naruto Uzumaki is able to conceal shuriken on himself and Ryūzetsu is able to conceal the fact that she is a woman.
Because most of the prison's population are shinobi or other individuals who can use chakra, neutralising them is very important and is the chief responsibility of Hōzuki Castle's master (主, aruji). Mui uses Fire Release: Heavenly Prison to seal prisoners' abilities and reduce their bodies to ash if they move too far away from him. Kahyō uses Ice Release: Earthen Consecutive Chains of Ice to force prisoners to dedicate all their chakra to keep themselves warm or risk freezing to death. Because Mui and Kahyō can activate their techniques remotely to kill prisoners, life within the prison is typically quiet and inmates try to avoid causing trouble.
Prisoners are let out from morning to sunset for daily exercise and meals, and at the end of the day they are instructed to return to their cells for sleep. Regulation 23 states that any attempt to escape the prison or to cause trouble result in three days in solitary confinement in the disciplinary cell. Clause 6 states that second time offenders get five days, third time is a week, and a fourth is permanent.
In Naruto the Movie: Blood Prison, Kusagakure originally built Hōzuki Castle in order to hide the Box of Ultimate Bliss; its function as a prison was the explanation given to the public. The Box is kept in a laboratory hidden deep underground, accessed through a stairway hidden behind a bookcase in the master's office. Prisoners are secretly used as test subjects by having their chakra sucked out in order to try and open the Box. Mui frames Naruto Uzumaki for several assassinations so that he is sent to Hōzuki Castle and the the Nine-Tails' chakra can be used to open the Box and release his son, Muku. Despite the attempts of several spies hidden within the prison population to stop Mui, he is successful. However, Muku is corrupted by the Box's powers and serves as Satori's host. He is eventually defeated, but Mui dies and the castle burns down. The escaping prisoners are recaptured by the Konoha 11.
In Kakashi Hiden, Mui died several years earlier during a joint operation by Konohagakure and Kumogakure. In the years since then the villages of the Five Great Shinobi Countries have alternated security duties until a new master for Hōzuki Castle can be found. The Ryūha Armament Alliance assaults the prison in an attempt to break out their leader, Garyō. Konoha thwarts their attempt, though cannot prevent several civilian casualties and severe damage to the prison's structure. Kahyō, the highest-ranking conspirator to survive the failed jailbreak, is offered a deal by the Sixth Hokage: in exchange for not being given the death penalty, she must serve as the master for Hōzuki Castle for the rest of her life. She accepts, the other Kage approve her appointment, and as a result the villages no longer need to provide guard duty.
- The castle is surrounded by the hōzuki plant, also known as Japanese lantern. In Japan, its seeds are used as part of the Bon Festival as offerings to guide the souls of the deceased.
- The sculpture behind the security desk is the Ecstasy of Saint Theresa by Bernini, which illustrates a moment where divinity intrudes on an earthly body.
- Despite being in Kusagakaure — which is in a landlocked country — Naruto the Movie: Blood Prison depicts Hōzuki Castle as lying on a cliff, by the ocean.
- The concept of the Hōzuki Castle's terrain is similar to Alcatraz, which is also situated near a cliff with a raging ocean beneath.
- In Naruto Shippūden: Ultimate Ninja Storm 4, Hōzuki Castle and Kahyō taking over as its lord are mentioned in the Shikamaru's Tale Adventure Mode DLC (which is set after the events of Kakashi Hiden: Lightning in the Icy Sky). As a result of Kahyō becoming its new lord, it is revealed that rate of secondary offences within the prison had dropped significantly.