LogFAQs > #933449398

I had a look at the achievements and looks like finding the culprit is also interactive?
Jotting down some notes now.

First twilight

-Discovered at 6:00 in the morning
-Gohda found the dining hall locked up
-Kumasawa arrived and they unlocked it with a master key
-Eva, Hideyoshi, Rudolf, Kyrie, Rosa, Genji are dead
-Children confirm the death of their parents; Kanon and Nanjo confirmed Genji's
-No one made a mistake (really?)
-Instant death
-Closed room with doors and windows locked, nothing suspicious in the dining hall
-No one hiding in the dining hall
-All doors can only be locked from the inside, or outside if you have master key
-1 master key for each servant, can't be used by anyone else
-Destroyed Genji's master key after they found the body