Otoko wa Waratteita

A case from 12 years ago in which a teenager murdered his parents. A few days after the incident, the teenager began to display a smile that looked as if it had been pasted on his face. Now, Aki Isshin, a reporter working for a small web media outlet, sets out to uncover the truth and heads to the flower shop where he works to interview him, but… (Source: Shueisha, translated)