After a month of playing the game I have to give it one star, I'm not against paying in gacha games, but normally you pay to get stronger faster and make your progress much easier, but in this case if you don't pay you make no progress at all! This game is not F2P friendly, the rewards are incredibly low and the ONLY way to make your units stronger is merging them, so when the early rewards run dry, you're stuck with no way to progress. Terrible game desing!