Determined to pursue his glorious childhood dreams, 30-year-old Rick Gladiatol, a modest clerk in the adventurers' guild, is offered a once-in-a-lifetime opportunity after he fatefully encounters the dark elf Reanette Elfelt. Reanette happens to be an elite adventurer of the legendary party Orichalcum Fist, whose members welcome Rick under the condition that he follow a Spartan training. Two years later, Rick is finally ready to take the E-Rank exam officially qualifying him as an adventurer. However, raw magical power can only be developed until one turns 20. As such, Rick faces the general hostility of fellow participants and examiners alike, leaving him no choice but to show the world that his hellish training has turned him into an invincible warrior.

One hundred thousand years ago, he was the founding disciple of the Tianlan Sect, his master ascended to the top, and he was refining Qi. Ninety thousand years ago, his martial nephew ascended, and he was refining Qi. Fifty thousand years ago, the old dog who was the gatekeeper of Tianlanzong also ascended, and he was still refining Qi. Thirty thousand years ago, the old tree at the foot of the mountain also became a demon, and he was still refining Qi before he could pass the catastrophe. Ten thousand years ago, Zhang Wuji, the 9872nd generation disciple of Tianlanzong, also ascended, and Xu Yang silently refined Qi. He retreated for 10,000 years, and finally, he broke through the 9999th floor of the Qi refining period! Ten thousand years later, he broke through and came out!

Shinichi Kudou, a high school student of astounding talent in detective work, is well known for having solved several challenging cases. One day, when Shinichi spots two suspicious men and decides to follow them, he inadvertently becomes witness to a disturbing illegal activity. Unfortunately, he is caught in the act, so the men dose him with an experimental drug formulated by their criminal organization, leaving him to his death. However, to his own astonishment, Shinichi lives to see another day, but now in the body of a seven-year-old child.

Perfectly preserving his original intelligence, he hides his real identity from everyone, including his childhood friend Ran Mouri and her father, private detective Kogorou Mouri. To this end, he takes on the alias of Conan Edogawa, inspired by the mystery writers Arthur Conan Doyle and Ranpo Edogawa.

Detective Conan follows Shinichi who, as Conan, starts secretly solving the senior Mouri's cases from behind the scenes with his still exceptional sleuthing skills, while covertly investigating the organization responsible for his current state, hoping to reverse the drug's effects someday.