Reflection room... Ah so japan, a "civilized" society condones torturing it's citizens. Hardened criminals might deserve it but someone who smokes weed does not.
May as well be an american prison at that point...
the problems of the japanese prison system, as well the entire judiciary (police and courts) are well known and can easily found with a short research... It's worse then what is actually presented here (even if some things may vary and depend on the specific prison or the prefecture managing it).
Even police interrogations can often being called torture... you can be hold for a lot of time, and be denied food,water, and going to the bathroom. This technique is often used to extort confessions (with sometimes people having confessed to crimes they never committed) that are then used in later proceedings (not everyone case do actually proceed to court however,even with a confession).