Basically, the game system:
Up to 15 girls unlockable with different classes. Equipment system (with differents stats like CDR, attack speed, and so on). Free gacha, with a bit more than 3 draws per day (1 draw per 7H, stackable trice). Village with several building, increasing damage with a specific element, increasing inventory, increasing stamina bar, increasing gold gains, and increasing maximum money you can hold.
The stamina is 1 per 5 min, completly refill on lvl up. The base is 25 stamina max, but each lvl of the dedicated building increase this cap by 5.

Missions have variable stamina cost. The first ones cost 5, grants 200 gold (before multiplier), white (trash) equipment and several crystals of a given element. The first boss cost 10, has 1H cooldown, grants 1000 gold and can drop blue tier equipment (5% chance). The next missions cost 6 and grant 250 gold (so the ratio is a bit better). Couldn't go further before the shit hits the fan.

The gameplay is a bit strange. Missions have 3 stars. One if you complete it, one if you kill every foes (you just have to kill a target to finish the stage), one if nobody die in your team. A character dying can come back after 12 or so seconds. You can't control how characters are moving or attacking, but you can move them to the back (if they are going the wrong way or if the are taking too much damage). Every character has a skill, usable after few second.