“A completely undetectable poison that kills 24 hours after consumed.” It is the rumour that has spread on the internet of a lethal drug that makes the perfect crime possible. It has even become a topic at the Tokyo Metropolitan Police Department’s Special Crimes Unit which Sasamoto Naomi has been transferred to. The background of Professor Matsui Toichi who invented this poison at an East European university is obscure. What is known of him is a fuzzy picture on the internet and the digits inscribed on the back of his hand. Matsui has disappeared but starts to appear before people who are trapped by their problems and hands them the poison. “You are free to use it as you will,” he would tell them...