Yami no Bansosha Season 2: Henshucho no Joken

A legendary manga editor who once took the world by storm plunges to death from a building rooftop. The police quickly classified it as an accident because there was neither a suicide note nor any reason to suspect foul play. However, there are many riddles surrounding his death. His editorial staff and the people around him say he deserved to be killed. Was it murder or suicide?
Investigator Mizuno Yuki teams up with Daigo Shinji, who happens to take over as the manga editor, to solve his death. Their clue is an old manga manuscript by an anonymous author that the late manga editor left behind. The two of them pursue the investigation and eventually get to the unsolved Shimoyama case, which was the biggest post-war mystery.
(Source: JDramas)