Hozuki Castle is a prison run by the Hidden Grass, well known for being notoriously difficult to escape from. Boruto and Mitsuki are sent there to protect Kokuri, a former member of a brutal band of robbers known as the Mujina Gang who's now targeted by assassins after betraying and deserting the gang.
The Celestial Prison has been embedded
in each of you to bind your chakra.
كما تمّ غرز السجن السماوي في 
كلّ منكم لتقييد التشاكرا خاصتكم
Das Himmelsgefängnis, das ich
in euch einbettete, ist eine Chakra-Fessel.
Prisión Celestial
Tenrou son unas cadenas
que atan vuestro chakra.
La Prigione Celeste che vi ho impresso 
farà da sigillo per il vostro chakra.
A Prisão Celestial foi colocada em cada
um de vocês para prender seu Chakra.
«Небесная тюрьма» внутри
 свяжет вашу чакру.