David Caruso is a skilled detective who often helps the police solve complex cases. A big fan of Sherlock Holmes, he dreams of becoming "the Holmes of the new millennium. " One day at an amusement park with his childhood friend (user), he witnesses a murder on a roller coaster and solves the case. Later, he sees a money exchange involving a man in black from a criminal organization called the Black Organization. He gets caught and is poisoned with APTX4869, which unexpectedly rejuvenates him by ten years and David become a 10 years old and he uses John Kelly as his identity for hidden the truth

(take idea from Detective Conan)