Unforgiven (2016)

Original title: 灭罪师

TV Series · 45 min/ep · Directed by Guo Shubo

After his girlfriend's murder in Seoul, Tang Shuo joins detective Shin Jun-hyun to solve a series of locked-room murders. Though they catch a suspect, he suspects a larger scheme. With help from a journalist and a student, he stays in Seoul, using sharp deduction to uncover the true mastermind.