I think she was that good of an actress. We know she's really smart and Yotsuha genuinely believed that she was her best friend for a long time, even before she knew about Uichi's situation.
In the same chapter you gave as an example, the reader doesn't see her face in page 9, maybe she was...
After re-reading this chapter, I just realized that the page 11 was supposed to show that she was pregnant (her water broke given the state of her legs).
Harusa was supposed to be the name of her child with Butama. I don't know if the child is alive or she faced a miscarriage and is delusional...
So the true destruction will finally begin. The book will surely sell given all the bad press Karin and Kinjo have received and reputation in Japan is more important than most countries in the world.
She's pretty much done for and there's no way to bounce back from this, it would be too...
The mom's picture cannot be a selfie because she wasn't holding the phone, and I doubt her daughter would take her photo knowing that her "soon-to-be" boyfriend is in contact with her.
Who's the lucky one taking the shots?
Of all the isekai I've read, this is one of the rare ones where the real world actually has importance for the MC and the other characters and not just a convenient tool to explain why the MC is more powerful than the others, I like that a lot.
Despite his vengeance and the dark powers he has acquired, he's still human at heart and feel compassion just like the others.
It's certain that after this event, there will be a high chance for their hearts to be tainted, quite a shame.
R.I.P the mother and the others.