Monetization model are similar to Azur Lane, where you will mostly buying skin, which rather high quality. Tits and Ass, you know them. As for the units in this game, in term of how easy for yoy to collect them... It was super easy, Most of SS units dropped from stages as long as you know what you were doing with team building.
I can't say this much better, it is really fun to build team to finish particular stage that crap on your previous team.
There is actually auto battle in this game but you have to unlock it first. You dont have to but you can.
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