Based on my post, I've come up with a few suspects. My four most suspicious players are Theodore, Aigis, Junpei and Koromaru.
Aigis and Theodore are most likely both mafia. They both voted for Yukari together on Day 1 within twenty minutes of each other. At the time they voted, she had already had 3 votes on her. Their two votes essentially guaranteed she would be lynched.
This isn't the first time the two have worked in tandem. At the start of the game, Theodore asked me to clarify my reasoning for suspecting some players. He voted for me over this. I responded by trying to provoke him, as I felt his reply was rather insecure. It seemed odd that he would go so far as to vote for me over my "suspicion" considering I had yet to even name a single person I was suspicious of. In response to my reply, Aigis also voted for me. Her reasoning was that I was evading the question and vote, which had the explicit purpose of provoking me. However, she would later go on to criticize Shinjiro for doing this exact thing.
Their apparent teamwork has continued today, where they are both suspecting me and Theodore is once again voting for me.
Conclusion:
Theodore and Aigis are by far the most scummy players in this game. If one flips mafia, the other is also likely to be mafia. They seem to have been working together from the outset, with Aigis in particular willing to contradict herself in order to throw more suspicion onto me. They probably thought I would be an easy lynch on Day 1 for my aggressive playstyle, but when Yukari came along they had another scapegoat to use. It's likely they probably thought they had thrown enough suspicion on me to get me lynched today as well.
I'm willing to take the risk on one of them being mafia.
##Vote: Theodore