However, Muku is corrupted by the Box's powers and serves as Satori's host. Despite the attempts of several spies hidden within the prison population to stop Mui, he is successful. Mui frames Naruto for several assassinations so that he is sent to Hōzuki Castle and the Nine-Tails' chakra can be used to open the Box and release his son, Muku. Prisoners are secretly used as test subjects by having their chakra sucked out in order to try and open the Box. The Box is kept in a laboratory hidden deep underground, accessed through a stairway hidden behind a bookcase in the master's office. 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.

Clause 6 states that second time offenders get five days, third time is a week, and a fourth is permanent. 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. 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. 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.

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. Mui uses Fire Release: Heavenly Prison to seal prisoners' abilities and reduce their bodies to ash if they move too far away from him. 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.īecause 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).

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.

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.

Naruto blood prison ryuzetsu