Hōzuki Castle

, also known as the, is a large castle that serves as a criminal containment facility located in Kusagakure, that appears in Naruto 5: Blood Prison. Its is Mui, who uses the ultimate imprisonment technique to seal the abilities of his prisoners.

The castle is situated near a cliff, where beneath is a raging ocean with tremendous currents that will wash up any attempt escapees and drown them. This, along with the imprisonment technique threatening to reduce anyone who reaches a certain distance from Mui to ashes, makes escape virtually impossible, despite the prison guards showing ineptitude in keeping the prisoners in check. The prison has no regard of the prisoners' circumstances of being sent there, and outside of the convicts' death, allows them to leave only if the village of the prisoner in question sends an official request for release.

Plot Overview
Naruto Uzumaki was sent here after being falsely accused of attempting to assassinate the Fourth Raikage, and killing jōnin from both Kirigakure and Iwagakure. This was all part of Mui's plot in order to use Kurama's chakra to open the Box of Ultimate Bliss to release his son Muku. Several prisoners, such as Ryūzetsu and Maroi, were in fact sent in as spies to prevent Mui from opening the box again. Ultimately, they failed to prevent that, and when Muku came out, he was corrupted by the box's powers and transformed into Satori. After a brutal battle, Muku and Mui died together, and the prison castle was burned down. The prisoners, being freed from Mui's imprisonment technique, attempted to escape but were recaptured by the Konoha 11. Mui and Ryūzetsu's bodies were buried outside the castle, while the box was cast into the ocean of the island.