The novel is an action comedy(?) if that makes sense
The hero is a girl and the church doesnt know. The king and a few high ranking members know and that is the reason behind the party.
As for why she is hiding her sex is because all the gear they have is the previous hero's gear and also to give false leads to the church since she hates men due to stuff happening before she was summoned
The premise of the story is that there 3 sides to the fight against the demon lord:
1) There is the hero party that is leveling up and is needed as only the hero can easily break the barrier that high ranking demons have
2) There is the kingdom that wants to stop the expansion of the church and get the achievments of the hero
3) And finally the church where a lot of the high ranking and high power members are very fanatic and stop at nothing to destroy the "filth"
The MC is from group 3 trying to do 1 since he knows they cant defeat the demon lord. And the story revolves mostly in the MC trying to guide the hero party into faster and safe leveling, but it doesnt work that way most of the time due to the fact the heroine has a major justice boner from before and now has the power to act on it