interesting,
the next update will be flashback story between MC and his Sister?
Would make sense to me because I have a theory or two (for what it's worth):
1 - Sara is a little devil, she controls her dad and her girlfriends like a puppet master. She is the one who decides when they can f*ck together and with who else he is allowed to f*ck. Plus, she doesn't seem to like her mom much, she's enjoying the fact that she can keep
daddy for herself without her mom in the way. So, what if she secretly contacted Karen and told her the whole truth? Karen would then contact MC's sister because she knows there is an incest (bro/sis) history running in the family.
2 – Karen was on her way to join them without telling them (a surprise visit), but when she got there she saw her husband f*cking her daughter and turned back. See theory 1 for the rest of the story regarding MC’s sister.
Theory 1 looks quite solid to me because the more the story progress, the more Sara shows her true face and her possessiveness (see how aggressive she quickly became when she learnt that Lana visited MC without her consent).