Boogiepop wa Warawanai, Higurashi no Naku Koro ni Kai Recommendations
Both anime tell a stoy in a non-liniar fashion. The stories skip back and forth through time, and nothing really makes sense until near the end.
Both Boogiepop and Higurash kai have a similar build up. Plot twists and multiple points of view are nothing unusual for these anime. Even though Boogiepop is weirder and harder to keep up with, the atmosphere in both is very dark and frightening.