[Siren changes her mind. She mildly regrets not getting to know Kaoru better whilst she was around. He's much more enjoyable company.]

Perhaps. But somehow I think it seems a little too easy to believe that he's the Mastermind. You would think he would have put himself in the suspect pool at least once. There were cases where suspects were ruled out immediately with substantial evidence. He would have benefited from something like that far more than never being a suspect at all.