And what really says that blonde dude couldn't be the same? He literally ordered them to get a hotelroom or something in that way. Especially darkness should get wet like a waterfall at this.>>152151337
No they don't, I can imagine that it develops into a "love-hate" relationship but no, at the start they pretty much hate each others guts.
Also most of what you listed there are just assumptions, which also begs the question, couldn't they get all of this more effectively if they just went with the blonde guy?
Aqua having a lot of money to spend, Megumin could use her explosion magic on much better targets well and darkness could still get abused by him. Though I gotta say what the MC does to her is, if you ask me the least abusive things in comparison to the other girls.
I mean she just moans when he denies some random shit of her. So I don't see why blondie with big sword couldn't do that too.