It makes sense evolutionarily as a woman to want your brother to have as much sex as possible since that gives you many nieces and nephews who share your genes.
She literally said “Onii Chan, I love you”, he cannot be so dumb that he thinks she wasn’t saying it to him, especially after earlier that day when she said she doesn’t hate him. I get the romcom dense MC trope, but this is just denial.
You’re right, it really did go off track. Did the author not know how to finish the incest arc and just decided to pretend it never happened?
Maybe Mihari put abortion pills in the cookies, but then how would Momiji be in on it? I doubt she would be able to tell Momiji that she knocked up Mahiro.
Yeah, you have to keep going, you cannot just drop the incest pregnancy chapter and disappear for a month.
What comes next? Motherhood? Abortion arc? These are questions that must be answered very soon.
If she’s the last of her kind the only way to preserve her species in some form is for her children to practice incest. They’re already going to be 50% human, if they don’t resort to incest her descendants will barely be spider people after a couple of generations.