I still believe ~Tameiki~ Lyrics - Detective Conan

I still believe ~Tameiki~ Lyrics - Detective Conan belongs to the anime Detective Conan, take a look at the argument:

Shinichi Kudou, a remarkable high school student known for his unparalleled detective skills, has a knack for cracking the toughest cases. But fate takes an unexpected turn when he stumbles upon a sinister crime and finds himself entangled in a web of danger. Pursuing the suspicious culprits, Shinichi inadvertently becomes a firsthand witness to their illicit activities. However, instead of dishing out justice, he falls victim to their vile plot as they administer an experimental drug meant to end his life. Miraculously, Shinichi survives the ordeal, albeit with an astonishing twist. The once brilliant detective now inhabits the body of a seven-year-old child. Astoundingly, his intellect remains untouched, allowing him to maintain his razor-sharp mind amidst his unexpected transformation. Determined to keep his true identity hidden from everyone, including his dear friend Ran Mouri and her father, the esteemed private detective Kogorou Mouri, Shinichi adopts the guise of Conan Edogawa. Inspired by the legendary mystery writers Arthur Conan Doyle and Ranpo Edogawa, he delves into mysterious cases alongside the senior Mouri, quietly utilizing his extraordinary sleuthing abilities to solve perplexing mysteries while covertly investigating the enigmatic criminal organization responsible for his altered state. Enter the enthralling world of Detective Conan as Shinichi, now known as Conan, navigates the shadows, working tirelessly to uncover the truth and find a way to restore his original form. With each new case he solves, he edges closer to revealing the secrets that lie within the ominous origins of the dangerous drug that forever changed his life.

Now that you know the argument, take a look to another songs of Detective Conan also called Case Closed | 名探偵コナン