Who...!?

Summary
With Sakiko unmasked, she admits she is the glass man. When Bossun gets suspicious, he realizes that Sakiko is hiding something since Sakiko would have break a window from the industrial room arts room (it starts with "ko"). Sakiko reveals that someone is blackmailing her by releasing a photo of her in middle school, an overweight girl. Piecing the clues from Sakiko's story, Bossun figures out the real culprit is Saori.