In the near future, augmented reality has become a key part of daily life. A gentle middle school girl named Yuuko "Yasako" Okonogi and her family have just moved to Daikoku City despite rumors of people disappearing. There, her grandmother, nicknamed "Mega-baa," runs a shop called Megasia that specializes in illegal tools which interact with parts of the virtual world. Mega-baa also hosts an unofficial detective agency called "Coil," a group of children around Yasako's age who find and handle corruption of the virtual world. Yasako gets involved with the group when Fumie Hashimoto, a playful member of Coil, helps rescue her cyberdog Densuke after getting trapped in virtual space while chasing a mysterious virus. Also investigating these corruptions and viruses is an abrasive hacker named