Idolmaster: Xenoglossia centers around mecha and re-imagines the ten prospective idols from The Idolmaster as fighter pilots of those robots, with eight of them also posing as students. The large robots are called Immortal Defender of Legatee (IDOL) and their pilots are called Idolmasters. IDOL pilots have to be girls, and they have to be chosen by the IDOL itself.
The Moon was destroyed 107 years prior to the beginning of the story in an event called Lost Artemis. This event caused numerous fragments to fall onto the Earth, which killed about one quarter of the Earth's total population. The remaining fragments of the Moon which orbit around the Earth are called Kompeito or Confeito. Once a fragment falls onto Earth, it is called a Drop. If the Drop is big, resulting in a moderate threat to the Earth, then it will be called Mint Drop or Lemon Drop according to sizes. Humans found a special silicon on Earth, probably from fallen Drops, and started research to turn that silicon into IDOL cores, of which there are five. The IDOLs are named after Lunar maria.
Haruka Amami, initially unsure of herself, passes an audition to be a singing idol and she is sent to Tokyo to start a career in entertainment. She does not know that the agency that recruited her is actually a front for a big task force called Mondenkind which uses the IDOLS to save the Earth from falling fragmented pieces of the Moon. Mondenkind's job is to handle any Drop that is bigger than Lemon-class. While the other countries of the world have missiles to handle Drops, Japan is currently the only country which uses IDOLs to destroy Drops. Yukiho Hagiwara and Iori Minase, who also want to be idols, are also taken into the same task force.
