In the near future, augmented reality has become a significant aspect of daily life. A young girl named Yuuko "Yasako" Okonogi and her family have recently relocated to Daikoku City despite rumors suggesting that individuals were vanishing from there. Her grandmother, nicknamed "Mega-baa," operates a store called Megasia that specializes in illegal tools designed for interaction with the virtual world. Additionally, Mega-baa runs an unofficial detective agency known as Coil, comprised of children around Yasako's age who investigate and handle corruption within the virtual world.
While exploring her new surroundings, Yasako encounters Fumie Hashimoto, a playful member of Coil, who assists in rescuing her cyberdog Densuke after it becomes trapped in virtual space while pursuing a mysterious virus. Alongside Fumie, an abrasive hacker named Yuuko Amasawa investigates these corruptions and viruses. The others refer to her as Isako.
Together, Coil endeavors to uncover the truths behind the enigmatic viruses and corruption. However, their pursuit may come at a considerable cost.
One of the awards won by the series was the Seiun Award in 2008 for the Best Dramatic Presentation category.