Have much stuff to play right now, so just tried Judgment out and did the prologue chapter. I really haven't played too much of Yakuza (I know, I know!) so apologies if some of this stuff appears in those games, but the gist of this game seems to be-
-"Open-world" type walking around, going into stores/arcades, etc. Just like Yakuza.
-Battles that also play like Yakuza. You have two fighting styles to choose from.
-Investigation segments where the camera goes into first-person and you need to focus on certain parts of the environment to find stuff.
-Following suspicious people of interest. You can run after them, but anything that alerts them will fill up a bar, that once full, is the end of the mission. You can stop and hide or appear to be doing other stuff on certain marked parts of the area.
-Chase segments where you hit buttons at the right times to dodge or go over/around stuff.
It's interesting to see a different take on the same game world as Yakuza. Despite you being a P.I., it still feels a little too Yakuza-ish-- your partner is Ex-Tojo clan, lol. Also for a guy who was supposed to be a hotshot popular lawyer, he sure seems fucking dumb- the story (This is right in the very beginning of the game) is that
spoiler (click to show/hide)
he got someone acquitted, which never happens, and then the guy turns around and murders his girlfriend and sets his apartment on fire. Uh...hope this leads to something like that guy having been framed.

Wouldn't make much sense any other way I guess.
There's also three 2P-only minigames you can play from the main menu: Puyo Puyo (modern version), Fighting Vipers (Arcade), and VF5 Final Showdown (Arcade). Am assuming you can play the CPU in-game.