The manga to Watanagashi-hen (2nd question arc) ends with these words from the author (original in Japanese, translated):
Watanagashi-hen, the second part following after Onikakushi-hen's scenario, focuses on explaining in greater detail about the events in Hinamizawa. Still following the once famous detective novels' style, Watanagashi-hen is the scenario that the original author himself likes the best in Higurashi no Naku Koro ni.
Noted as even more malicious than Onikakushi-hen, Watanagashi-hen is actually the mildest scenario in Higurashi no Naku Koro ni. Still, as it has been noted, there was a malicious trap by which once caught, the victim would be in great peril. Moreover, even the victim himself wouldn't notice that he had been caught in the trap.
Please confirm that in Watanagashi-hen's solution arc, Meakashi-hen.
...If by any chance did you know about being tricked into the trap... congratulations! You have enjoyed Watanagashi-hen to the fullest (LOL).
What is the malicious trap mentioned there?