Ep. 974: Conan deduces Kengo Aono is the killer using traffic signs and laws.

Conan identifies Kengo Aono as the murderer by interpreting Touko and Shiori’s dying message as a "no parking" sign, which combines "ao" (blue) and "no" to form "Aono." He links the number 7751 on Shiori’s phone to law article 71, section 5-5, which prohibits using mobile devices while driving, noting Kengo is the only suspect who violated this rule. Conan also deciphers Naeko’s message, revealing she is held at a planetarium. Kengo confirms his guilt, explaining that Aiko, his girlfriend, died because Touko and Shiori stopped him from saving her. Aiko’s final message causes Kengo to break down. Chiba triggers Kengo’s trap but is rescued by Naeko, whom he recognizes as his childhood friend. Kengo is subsequently arrested for the murders.

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