This should be a universal rule to stop creating shitty stupid scenarios:
"Don't try to make a 'Plot Twist' with a character you JUST FUCKING INTRODUCED IN THE SAME FUCKING CHAPTER"
That's so damn dumb. I wonder why this author even tried to hide the culprit with the black figure... only a 6 years old, who just started reading, would be fooled...
At first, I was like "Naaaw, it would be so dumb if it was her. This author just fooled me by making me think so. It's gonna be someone else".
Then she fucking appeared IN FULL SCHOOL UNIFORM... in the middle of the night...
Yeah, this story is getting pretty shit. I think I'll give this one more chapter to prove me wrong.