 If you liked
ChäoS;HEAd
|
 ...then you might like
Gakkougurashi!
|
Both of these anime have to do with characters skewed perceptions of their reality, and how those perceptions play into their lives. Chaos;Head focuses more on the concepts of paranoia and hysteria, while Gakkougurashi explores the vast field of psychological disorders. Both contain characters that may not actually exist.