LogFAQs > #932213699

It's interesting because, thinking about it, Tsumugi did an amazing job infiltrating the cast. She had to pretend she didn't know what was going on, she had to fake despair and sadness a bunch of times, and she nailed every single one.

I only suspected her because the universe itself avoided her and did not let her bump into plot events or be suspected by other people. So it's a 4th wall reason not a story one.

That said her murder plan was kind of weak. Expecting people to never get into her secret room when the game doesn't even have a rule against breaching doors (and not adding that rule in the first place) is very dumb. Announcing she was going to the bathroom was also unnecessary.