Ok, my impression is that Marisa left the kos fall to their death, but the Ko marisa survived and, parent Marisa like the child.
What i don't understand until someone translate is if Reimu stole the Ko, before caught by anon, and if the Alice was a random raper or was anon work too.
It was anon's work, you can see it in the drawings. He put the Alice there, and stole the Reimu's surviving baby, and (I think?) he punished that Reimu by sewing her mouth shut and sewing her butthole shut with the baby. Pretty neat and creative if you ask me.