People joking "lel who's these naked nuts" - this is not cheap fanservice, far from it in fact.
These are "Adamites", Christian nutjobs who were really involved with Zizka during the Hussite Wars. For more info, here --> https://en.wikipedia.org/wiki/Adamites
Anyway, I had lost hope for this manga, so thanks a lot
@Thelegendarytaeyamada for picking it up!