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 dōjin 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. Many of the current members reside in the Hokkaidō or Kantō areas of Japan.
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