The Professor + The Ending *spoilers*

(I'm going off subtitles so maybe there are subtleties that knock my argument on its ass but...)

IMO, the professor *beep* everything up. Had he hypothesized Misato (the daughter) having a role in the death, _i_would_hope_ that he would have understood the need for the case to rest as Ishigami planned (in order to protect Misato). Maybe he would still have a problem with the innocent homeless man being killed, but if he couldn't find the ex-husbands body in time [and presumably he couldn't and he knew this] then there would be no point in cracking the case since the body is required to prove his theory.

But instead he pushed Yasuko into a guilt trip. Even if him telling her "everything" (homeless man) was a bluff, we saw him atleast telling her he knew she was the killer which might have been enough to push her over the edge. This caused her to make an emotional scene at the end which unraveled everything and presumably *beep* up her and her daughters lives. Which in turn, ruins Ishigami's peace of mind/happiness (knowing Yasuko & Misato can get a fresh start on life).

My assumption is that Yasuko wouldn't have showed up at the end if it hadn't been for the professor talking with her

Hard to say if the professor was expressing _regret_ during the flash to him alone, against the door of the interrogation cell during the emotional climax.

Long story short:
1. *beep* the homeless guy, he obviously wasn't missed.
2. The professor should have suicided or something.

amirite or amirite?

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prepare to be boarded