Edit : The game is dead, sadly.
The music and character designs are AMAZING! The game may have some downsides, but it's still pretty enjoyable regardless.
Story is alright at first, there are some fun interactions. It only starts to actually get good later, starting from chapter 7. You will probably enjoy this more if you watch the anime(I don't). There are 10 chapters so far, so the story still has long way to go.
I've played over 30 invitations.. which is basically character side stories. They are mostly not as good as the main story and also not fully voiced. Side stories are locked behind the affection system, but it doesn't take that long to raise them.
The gameplay is pure PVE, aimed towards casual audience. The combat is simple, basically just casting skills and building energy of certain colors before casting your ultimate. Units attack from spesific spot and target enemies on spesific spots. A bit similiar to Darkest Dungeon, but there is no dynamic around movements because you can just move for free. The downside of moving is that it does not give you any energy, so your units are better when glued on their specifically designed position. A bit of wasted potential imho, it could be way more interesting. Some notable non combat aspects are the puzzle stages which is not bad unless you hate puzzles and "make a drink" minigame that you have to do if you care about affection level. It gets boring pretty quickly, though.
The biggest downside to me is actually the annoying bugs. These minor bugs are ruining the experience during my earlier days of playing. Fortunately, most of them are fixed already, so it's fine now.
In terms of graphic, the L2D models are nice, but 3D chibi models are not that impressive. There are some good animation scene in the main story which is nice. The thing I don't like the most is the UI. Aesthetically speaking it's not bad, but it just doesn't feel very convenient. I wonder what kind of genius decided not to show stamina and currency in the homescreen.
It has no sweep/skip/raid for grinding, but you can do auto battle in the background while doing other businesses, which is the next best thing. However, you can only auto farm one stage at a time(but you can choose how many stam to spend on said stage)
The gacha is alright. 75 hard pity with 1.5% rate. It has 50/50 and carry over. The total of basic monthly income is 27 pulls, and the current event rewards are pretty good.
8.2/10. It's decent. Still below Brown Dust II or Outerplane if I have to compare it to other recent releases that I've played. If you love classical music, the character designs, or maybe just a big fan of the anime, then do give it a try.
If you have decided to try this game right now, you are not too late. You still have two weeks for Titan's banner and her event, and there is also the upcoming Cosette's banner worth looking forward to.