I guessed it by thinking "Okay, No. 36 is really big on MindFucks. How can he MindFuck the Marisa into thinking ClerkAnon is helping, while causing Marisa to be the one to kill the babies?"
Also, notice that it's Marisa who's killed most of the family by now. Except for koReimu and koMarisa, and we're not sure if they're totally dead, or just in badly cripped state, tho I think koReimu's a lost cause by now.
I hope for one last MindFuck that will cause Marisa to kill koMarisa, causing her to snap.
The biggest challenge is for marisa to recognize it killed them. It didn't know why reimu died, and it'll wonder why Mr. Sweet juice isn't helping but not I caused their death.