The culprit is Keisuke Ogino. He sprinkle some used salt from his pocket in his beer to manipulate the time table of his alibi. He killed Daisaku Katsumoto because he published a false article that lead to the suicide of the actress it was about. Keisuke was disgusted at the disregard for the victim, and that the president only did so for sales, disgracing the company he was passionate to work for.
