Interesting concept! The cover art made me want to play this game! I have some feedback for how this could be even better:
-The name's shizuka & shizuko were both similar in name and color, so I had a hard time figuring out who was talking when.
I think some of the dialog could be condensed or trimmed and still convey the same message to move the story along quicker.
-Its hard to tell what emotions characters are feeling when everyone's face looks neutral and there are no additional sprites on screen. Having some sort of sprite on screen would help me see the character's emotions more.
-Sometimes the dialog over flows on a few lines, like this:
'...has this face that just makes..."
You could try cutting this line into 2 lines to fix this.
-To me it wasn't clear what was happening when the killer appears since it was a black sprite that wasn't facing the player's perspective, and the knife is fairly small to see.
-I also had trouble figuring out what to do when the killer appears. Some sort of specific hint for the player other than 'I have a plan' may have helped my confusion there.
-I think there should be a retry option if a player fails to do the cereal killer part correctly. Or a prompt to save just before that part starts, else it can be jarring to do all of the beginning stuff again in case a player forgot to save.
Would love to see what you make in the future!