The culprit is Yoriko Danno. She wanted to avenge her son death. When she was pickpocket a year before the series, her purse contained her car keys. Because she didn't have them anymore, her son who has asthma was locked inside the car for several hours. When they got to the hospital, it was too late and he died. So Yuriko researched that pickpocket on the internet and hung out of 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.
