Asami is a sociology student studying otaku for her thesis. Her relationship with Kotaro is on the rocks: she's busy with her research, and he's an aspiring filmmaker working on a J-horror flick. The real horror is out there on the streets: a serial killer who amputates body parts from his prostitute victims. What's his sick game? As Inspector Arakawa and his young protégé Ryohei wade deeper into depravity, Asami, with the help of cosplayer Maiko, sets out in search of an otaku so elusive he's almost an urban legend in the youth culture capital of Akihabara: the mysterious Buntaro.

Asami is missing. The Tokyo police have their hands full with a serial killer, so two people set out to find her: her boyfriend, aspiring j-horror filmmaker Kotaro, and her new girlfriend, cosplayer Maiko. Trouble is, he thinks she's shallow, and she thinks he's a stuck-up bore. The grudging team-up is getting nowhere fast, but neither are Inspector Arakawa and his young protégé Ryohei with their case. Still, Arakawa's been through enough darkness in his own life to know the city sometimes discloses patterns linking the most disparate events in the unlikeliest of ways. Can he perceive the pattern in time?