The culprit is Yoriko Danno. She wanted to avenge her son's death. Yoriko was pickpocketed by Ikuyo one year ago, and she lost her car keys which were placed inside the stolen purse. Because she couldn't open the car without them, her son who has asthma was locked inside the car for several hours. When he got sent to the hospital, it was already too late and he died. So Yuriko researched about that pickpocket on the Internet and hung out at places where she frequently appears.
Touhei Benzaki turns out to be Bourbon in disguise, while the pregnant woman is actually Vermouth, who is there to assist Bourbon.
