I Killed Someone...

The Protagonist Designed the Crime, No One Survived, Manslaughter

There is a novel in which the protagonist travels to a time to reduce the crime rate, so he organizes a live broadcast of solving crimes. The protagonist wrote the script of Manslaughter, Mekong River Case, No Survivor, and participated in it. After the completion, there will be an explanation from the police station. What novel is it? I forgot.