Exactly. I also have the theory their monitors don't work like ours. Don't you feel strangely sleepy every night? If the killer murdered Charles during the night, then their monitor didn't affect them.

[Dojima takes a saw, looking at the ridges and blade carefully]

I have checked all these tools but I have found nothing. We're dealing with a very meticulous killer.

[Sigh]

At least we have tools now. May as well give these good use.