Humanity Has Declined (人類は衰退しました, Jinrui wa Suitai Shimashita), or Jintai (人退) for short, is a Japanese light novel series written by Romeo Tanaka. The novels originally featured illustrations by Tōru Yamasaki for the first six volumes, but Yamasaki was replaced by Sunaho Tobe in 2011. Shogakukan has published eight volumes since May 2007. Three manga adaptations have been produced. An anime adaptation produced by AIC A.S.T.A.