wait how is the sister having an affair? the only thing i got from this chapter is that the sister has daddy issues that is also a possessive yandere for her brother...
You need some life experience...
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Still, this story is getting me wondering.
The mother and daughter combo certainly seems like they are working into finding guys, and likely taking stuff from them. One could guess that the daughter trying to seduce her dad could be a blackmail trap but... What she did with her classmate seems really heavy if the guy is just the current victim, although she could also be a bit of psycho taught by her mother, not really about her destroying the girl's family, but about her commitment to "protect" the step-father, would you do all that if you are planning to throw him away anyway?
The fact she is aware of such things also shows some understanding of adult life, so I guess she was well trained..
On the other hand, I could also imagine him being the "nice guy", the woman likely is already on her years, and could be considering stopping, and the daughter does all that due to their, or exclusive her, twisted "common sense" of how to keep a man attracted.
Then the sister with her own affair and problems is the one who can recognize her own characteristics onto others, although as MC pointed out, it seems she is a bit nagging pointing out measly faults, so although she may want to keep her older brother safe, she may likely be the type that pushes faults onto others, without recognizing her own responsibility.
As always, people with twisted senses are able to think that their twisted views are the normal, and cannot comprehend how they may be seen by others.
But it was a nice touch to add some fails to the sister.
And taking it that the translation of the contents of her phone are at least properly translated, the other person is likely her lover either accepting to either take her in, or to throwing some sweet words at her to keep on banging her.
So yeah, she is likely a cheater herself, who may recognize some of her own faults on the wife/daughter