So, the pocket dimension is what I could call a mix between Kamui and Amenotejikara (Sasuke's ability). Whilst the dimension of Kamui is in constant existence, and Amenotijikara revolves around replacing space with oneself, my ability (Jigoku No Azuma) creates a dimension which is an identical copy of an already existing piece of the real world, any size from 1 by 1 meter to 20 by 20 meters. From inside this dimension, people can see what is going on outside in the real world, but they cannot interact with it and technically speaking do not exist in that dimension. I refer to this portable dimension as a "territory". The only person who can leave this dimension at will (without other s/t jutsu) is the user. In this regard, it's like Kamui, since it creates a separate realm of the user's own design. However it takes part of the replacement aspect of Sasuke's ability to exemplify how it takes physical form.