Manner of Death, Vol. 1 (manga)

When the skilled coroner Dr. Bunnakit is called to examine the body of his childhood friend after her "suicide," he soon determines that she was actually murdered. That night, a mysterious stranger threatens him, telling him to rule her death a suicide-and after he confides in his prosecutor friend about this incident, his friend suddenly goes missing.

But all hope is not lost, as a young lecturer named Tan offers to help him get to the bottom of all this-which would be more reassuring if Tan weren't the prime suspect...