The Accidental Detective (2015)

Dae-man is a crime enthusiast who runs a power blog about the country’s biggest cold cases. He aspired to be a homicide detective but after years of failed attempts, he now runs a comic store. He walks on eggshells around his wife for failing to provide for the family. But he cannot help himself making daily trips to the police station. One day, his best friend and detective, Jun-su, is charged with the murder. Dae-man sets out to investigate to prove his friend’s innocence. Only the washed up Detective Noh offers to help his colleague in trouble. A cold case specialist blogger’s theory coupled with field experience of a seasoned detective and the two launch a joint investigation into their friend’s alleged murder.

Source: TMDb