In the not-too-distant future, augmented reality will be an integral part of daily life. Despite stories of people disappearing, a sweet middle school girl called Yuuko "Yasako" Okonogi and her family have recently come to Daikoku City. Her grandmother, dubbed "Mega-baa," owns a business called Megasia, which specialized in illicit instruments that connect with elements of the virtual world. Mega-baa also has an unofficial detective agency called "Coil," which is run by a group of children about Yasako's age that investigate and deal with wrongdoing in the virtual world. Fumie Hashimoto, a lighthearted member of Coil, assists Yasako in rescuing her cyberdog Densuke when he becomes stuck in virtual space while following a mystery virus. An aggressive hacker is also looking at these corruptions and infections.