IOSYS is a Japanese musical ensemble and dōjin circle from Sapporo, Japan. The group is primarily known for producing remixes of music from the Touhou Project series of doujin games. They are not signed to a label, instead preferring to release their music through dōjin channels such as the Comiket convention and via their website. Their music frequently parodies characters or themes of games such as those of Touhou Project or Atlus's Etrian Odyssey.

IOSYS is generally best known for the Flash movies that go along with their songs.

(Source: Wikipedia)