So is the game any good? What even is it?
should I watch the anime first before playing this?
It's a very fan-servicey visual novel, with LOTS of branching paths. Too many for my liking personally.
However, it's fully voiced, and goes lots of places. Your mileage may vary, but it's not considered a VERY good VN from the reviews I have seen.
The fanservice (especially the original voice actors!!) will be lost on you, in case you didn't watch the Anime.
One of the routes also partly spoils some stuff about a character that was introduced halfway through the first season of the anime, and the game assumes that you already know some stuff about the relationship / shared past of two of the detectives - so you might get spoiled on this, which I found neat to discover watching the anime (not a big spoiler IMO, but I'm not very sensitive to spoilers).
Overall, you probably won't try to get the true ending on this, unless you are a major fan of the anime or the visual novel format.
It's entertaining enough, but very long for people that just want to play it casually.
The voice acting is suberb though!
Also, fan-service. Wanna share a special moment with one of your favourite chars of the anime? Now you can! Some of them topless! (None of the girls though, lol)
Ah, and it has a Threes / 2046 minigame included, so if you like these, might as well grab it.