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.

An anime adaptation produced by AIC A.S.T.A., directed by Seiji Kishi, and written by Makoto Uezu aired in Japan between July and September 2012.

The story follows an unnamed girl who acts as a mediator between humanity and the "fairies" who are small elf-like creatures attracted by sweets and happy things, but also have the habit to cause trouble to her with their powers in their endless search for amusement.

[17] Another manga, illustrated by Takuya Mitomi, titled Jinrui wa Suitai Shimashita: Nonbirishita Hōkoku (人類は衰退しました のんびりした報告), was serialized in the same magazine from November 25, 2011,[18] to May 25, 2012.

[20] Mitomi also illustrated the four-panel comic strip manga Jinrui wa Suitai Shimashita: Nonbirishita Hōkoku 4-koma (人類は衰退しました　のんびりした4コマ), was serialized in Monthly Ikki from June 25 to August 25, 2012.