Translation on this would be great to help understand - It almost looks to me like this Reimu did some sort of deal with the human, but is about to find out that mister human isn't going to live up to his end of the bargain.
Basically she's a spoiled girl who is selfish and can't do anything on her own, and that's in yukkuri's standard. Her younger sister all can already shit on their own and don't need to ask to be licked clean by their parents anymore.
Moreover, she want to be the centre of attention, which made her ignorant about danger. Her family know to stay quiet when they hear human coming, but that Reimu just go out and talk to human.
Marisa is out to hunt, and when she came home, her family is all dead.
I strongly dislike the idea that "all wasa are inherently scum". That aside, I get that this wasa-Reimu's slow, torturous end was likely deliberately omitted just to raise the hackles of the readers, but it's no less annoying. The suggestion of what's to follow doesn't quite cut it for this one.