Kitsutsuki Tanteidokoro EP12 - Pale Blue Skies

With his condition rapidly deteriorating, Takuboku tasks Kyousuke with tailing a suspicious man they saw at the church. Takuboku is certain that a single criminal, Accuser X, is the true culprit behind the string of crimes involving accusatory letters which have exposed various social issues. Who is Accuser X, and what is that person's true objective?