「蝶は十一月に消えた 前編」 (Chou wa Ju-ichi-gatsu ni Kieta Zenpen) "The Butterfly Vanished in November, Part 1"

This is what we've been building up to all season - Sakurako-san's raison d'être. Truthfully, this show was beginning to lose me with these past few episodes, but this current case has me back on board once again.