Can't beat Stage 21!

Stage 21 is particularly tough for free-to-play players, right? Try placing your ranged units in the back and prioritizing the reinforcement of your defense units. I'm truly sorry about the previous matter, Hou.

I don't quite remember Stage 21, but with the priest's buff and the tank's debuff, use shotguns for firepower, and the machine gunner if you have them. Prioritize getting shotgun and machine gunner skills, and aim for infinite ammo. Also, make sure to grab blessings and boost the buff percentages.