Meitantei Conan OVA 09: 10-nengo no Stranger

Confined to bed with a bad cold, Conan overhears Sonoko urging Ran to stop waiting for Shinichi and consider someone who is actually present in her life. Soon afterward, Haibara offers Conan a new prototype antidote for APTX 4869. He takes it hoping to regain his old body, only to awaken as Shinichi in a world that appears to have moved forward by 10 years.

The Detective Boys are now teenagers, familiar streets have changed, and Shinichi learns that Ran has spent a decade waiting for someone who never came home. Worse still, she is preparing to answer a marriage proposal from Dr. Tomoaki Araide. Faced with a future in which his disappearance has reshaped everyone else's lives, Conan races to find Ran before she makes a decision he may have no right to stop.