Love this! Sprites and background are really well drawn. The gacha upgrading system really cranks up the addictive elements of this game.
I did encounter a bug where a new unit overlapped my badass old unit, and I can no longer deploy her (clicking on her just makes a invalid sound).
Also, I think it might be nice to add some elements that encourages trying out different units. Maybe just a random stage buff/debuff that applies to categories (eg. all fluffy units attack increase by 20% this round), and it warns me during character select screen so I can prepare for it.
Great job overall! Had alot of fun playing, thanks for making this!