Its literally the same combat mechanic we saw in the Reimi
, you need AP to use skills, you get AP by letting your ATB fill.
You also have special bar now beneath your health, that is used by special ammo in addition of AP.
JSK even put a guide on the text file accompanying the game about the combat mechanics.
But here is the combat window in english.
In the demon queen, you just had to cum loads of times inside her between the fights.
In MGB, I have no freaking clue, as you can only cum inside 3 times on each story, it may have to do something with rape ending and the amount of cum you have set on your settings.