Mainly skipping the 'middle part' because clearly no mindfuckery is gonna happen there in this sort of story.
But in the 3rd part start apparently after dude's 'raped' the mom and turn out both were drugged by the daughter who's showing some yandere level emotion here.
And the mom finally confessed that she's his kid, the one he thought she aborted, but she didn't.
The girl then talk about how her mom's company was having issues, then one day on her way home she got pulled into a car and raped by some old man who talk about 'compensation'
After which her mom's company did better, and the guy remembered 'oh yeah, the first time I did her there was no blood'
Kinda skip the rest of that to the ending, where the girl was hugging him but he have emotional outburst that can be summarized as NOPENOPENOPE
she did not take it well. screaming about how even though he promised to make her happy...and pulled a knife
next thing we see the 3 together as a happy family
and the guy had some internal thought about how that might've all been a dream
until he seem the background on his phone being the picture at the end of ch 1 here
and suddenly how the mom and daughter was portrayed shifted to be more...screwed up.
and end
There's one frame image showing framed photos that seem to imply he eventually impregnate both of them though.