I investigated Alice last night, and the result is Innocent. Here's a the result of our investigations so far:

Day 1:

Mamizou said: Alice is a traitor

Alice said: Kotohime is innocent

Kotohime: Koishi is a traitor

Merlin said: Koishi is innocent

Koishi said: Mamizou is innocent

Day 2:

Mamizou died

Alice said: Merlin is innocent

Kotohime said: Alice is innocent

Merlin said: Alice is innocent

Koishi said: Alice is a traitor

---

Assuming Koishi's telling the truth, Alice is the traitor, endgame. But if she is, then...

Koishi: Definitely Sane

Merlin: Definitely Naive

Kotohime: Definitely Insane

Mamizou: Definitely Paranoid

Everything fits. If Koishi's lying (and therefore, traitor) then...

Alice: Definitely Sane

Merlin: Definitely Naive

Kotohime: Definitely Sane

Mamizou: Paranoid

It doesn't fit, therefore this proves that Koishi is innocent and Alice is a traitor. Besides, I don't think a scum would lie her investigation outright before thinking this all over. However, Alice manage to say the exact line of the result PM, which makes her more likely innocent.

Then again, she might be able to adapt it from Kotohime's investigation

Kotohime wrote:"Wait, guys!" Kotohime blurts out, "I've got it! Because... Because I did some 'criminal investigation' last night," she announces, using a creative term for 'Breaking and Entering', "and lookie what I found! This solved everything, right? Just take a look!"

My investigation shows Koishi Komeiji to be a Traitor.

But it would be heck of a gamble, and I don't know if any scum is daring enough to do that.

... Unless she asked Rin what the exact line of the result PM is. It's more of a game mechanic question, so she might get an answer.

Okay, I am overthinking this. If nobody can point out the hole in my logic, I'm going to vote for Alice.