According to Suguru Geto, Prison Realm is a living prison and the final remains of a Buddhist monk named Genshin. Prison Realm has the form of a cube when its power are sealed. To unlock this cursed object, there is one condition that need to be fulfilled. Once unlocked, there is nothing Prison Realm can not seal. However, Prison Realm could only trap one object at a time, unless the object within the Prison Realm either die or perish while trapped inside it.
To unlock the Prison Realm, the target must be within four meter radius for one minute or more specifically, one minute inside of the target mind. Once the condition has been fulfilled and the command 'Prison Gate, Open' is given, the Prison Realm will expand into a mass of flesh with a big eye in the middle and the cubes remains become its border. Once the target has been captured by the Cursed Object, the Prison Realm will revert itself (along with the imprisoned target) into its sealed state once more once the command 'Gate Close' is given, albeit now several eyes will adorn the cursed object.