Blue Drop (ブルー ドロップ) is a Japanese science fiction yuri manga created by Akihito Yoshitomi. It comprises five chapters that were serialized in the shōnen manga magazine Dengeki Comic Gao! from June 2004 to December 2005, and later collected into a single volume. In 2007, Yoshitomi began to work on a new Blue Drop manga, titled Blue Drop: Tenshi no Bokura (BLUE DROP ～天使の僕ら～), which was serialized in the manga magazine Champion Red between February 19, 2007, and January 19, 2008, with its 14 chapters later compiled into 2 volumes. Each volume contained a chapter of another series called Tenshi no Itazura (天使の悪戯) where Kasagi is a member of an alien race of females called the Arume. She spends her time playing matchmaker for unsuspecting, cute human girls. The third and fourth chapters were not released until 2008.
A Blue Drop anime series directed by Masahiko Ohkura and produced by Asahi Production and BeSTACK aired in Japan between October 2 and December 25, 2007, under the title Blue Drop: Tenshitachi no Gikyoku (BLUE DROP ～天使達の戯曲～). The first DVD release on December 26, 2007, was accompanied with a bonus 6-chapter manga volume called Maiorita Tenshi (〜舞い降りた天使〜). In 2008, two drama CDs were released. The first, released on May 23, was titled Lover Side, and included the third chapter of Tenshi no Itazura. The second, released on June 27, was titled Traitor Side, and included the fourth and final chapter of the Itazura one-shot series.
All the Blue Drop stories revolve around a war between humanity and the Arume (アルメ),[1] an alien race consisting solely of women. Both manga series are set after the war while the anime is set before. The two manga series feature some degree of sexual content; the second manga being considerably more explicit than the original one.