Fast paced combat, easy to get into if you're used to Hack 'n' slash games like DMC, MGR or the like, each character (Construct/Omniframes) has it's own gameplay/mechanics, so there's quite the variety to choose from, story-wise; each one of them has their own personality and backstory you can get attached to, the game also is not really demanding in terms of Phone specs, you can always tinker with the graphics to make it more easy on your device, the game also has a PC Client if you're not that into the Mobile gaming experience.
The upgrade system of the characters is the one you already know from the Gacha scene; get a character more than one time and you can upgrade it further, ex: get an S Rank, and then get another copy to get Shards and then use them to upgrade it to SS, and so on, same goes for A Ranks, so getting the same thing in the Gacha over and over is not that bad at the end of the day, specially if its a Character you like, and every character have their own Ascension Skins as you upgrade them, you can also buy some of the Skins with free currency (some of them are non-farmable), this is a Gacha game after all, so don't get surprised that the best Skins with special effects and the like are paid-only, altho we do get some Event Farmable ones from time to time.
Gacha-wise; the game is extremely F2P if you're just going for the Characters in their base rarity (S Rank; a 5* if you may), the A Ranks (4*'s) however, come in quite the amount as you roll in the Gacha for your desired S Rank, so you will end up with A Ranks with an upgraded rarity, there's also Uniframes/Transcendants who are S Ranks, but you can get them in one Multi on the Gacha, you can mix and match them with the other Constructs, but you'll see the downsides of doing so in-game when you get to it.
Doing your dailies and various Events will give you enough currency to get the newly added S Rank in each Update, if you want to spend money to get Shards (Shards to upgrade any S Rank to SS can be obtained via farming in-game) to upgrade your S Rank further, or to get 6* Weapons (powerful, but not neccesary if you're not going full meta/competitive) that's entirely on you, there's no need tho, later we also got introduce to CUB's, which is like Pets for the characters (some specific to each character), they do boost the overall performance of a character, but not necessary all things considered, they're really cool tho, you can farm for them too.
The music is powerful and beautiful at the same time, the story is soooo good, engaging and dramatic and just gets better with every update, the overall aesthetic of the game is quite charming if you're into the NieR Franchise, or the overall post-apocaliptic scene.
If I have to list downsides it would be that farming is kinda repititve, you basically repeat the same Stage, get the Event currency and spend it to get Materials, pretty standard but I can see people getting ticked in the worng way by it, but that's only for the Materials, each Patch comes with different Modes that require playing, some Challenges and some are mini-games, there's always something to do.
Definitely a must try 😌
Edit: It's been over 2 years since I started playing this game and things just get better and better, do yourself a favor and please try this game, in KuroGames I believe 🛐