Higurashi When They Cry: Time Killing Arc, Vol 2

Following a lead on the kidnapping of the construction minister''s grandson, Officers Ooishi and Akasaka spot a secluded outpost station that shows signs of recent traffic. A little poking around brings them face to face with the boy''s abductors, and the criminals aren''t going down without a fight. Once the boy is recovered, the dam project is put on hold, and it seems to be a happy ending for everyone. What could Rika''s warning possibly have been about . . . ?