After remembering that Japan’s signage system is based on England’s, Conan concludes that Kengo Aono is the serial murderer. Touko and Shiori’s dying message was in fact the “no parking” sign. Blue in Japanese is “ao”, and no parking signs are “no” layered on top of a blue sign. When combined, they form “Aono.” The “7751” on Shiori’s phone meant law article 71, section 5-5, prohibiting any persons using or looking at their mobile devices whilst operating a vehicle.