The setting is, basically, what happens when you collide America with Japan really really hard. Although ostensibly the locales and people are Western, the law system, with its brutal guilty until proven innocent nature, lack of a jury, and "speed the criminals through to a conviction" style, is thoroughly Japanese, as is the unspoken assumption that it is somehow remotely possible to get where you need to go in California with only a bicycle.

There is a mild spiritual/psychic undercurrent to the world. Spirits exist and can be channeled by spirit mediums, and strange powers can tap into the human psyche and enhance senses, or detect coverups. These powers are rarely discussed too much, although the level of belief displayed in them varies. Presumably, since the setting is rumored to be the same world as Ghost Trick, there is also the capacity for ghosts to manipulate the world around them as well with enough effort.