Den-noh Coil, Coil — A Circle of Children, is a Japanese science fiction anime television series depicting a near future where semi-immersive augmented reality technology has just begun to enter the mainstream. The series takes place in the fictional city of Daikoku, a hotbed of AR development with an emerging city-wide virtual infrastructure. It follows a group of children as they use AR glasses to unravel the mysteries of the half real, half Internet city, using a variety of illegal software tools, techniques, and virtual pets to manipulate the digital landscape.

Den-noh Coil, in development for over a decade, is the series director debut of Japanese animator Mitsuo Iso. It premiered on NHK Educational TV on May 12, 2007. Due to the animators involved in its production and its unusually high-profile television broadcast time slot, Den-noh Coil was highly anticipated.

Mari Wakatake has been living with her Grandmother for the past 5 years after a tragedy caused the loss of her home, friends and family, as well as her memories. Fearing for her future, her Grandmother admits her into Kaihou Academy, for her to make friends, instead of home studying. Although reluctant to go, she does and meets Hagino Sekonji. At first appearance, this girl appears like a normal student but inside her lies a deep secret that relates to the tragedy of 5 years ago.