Three classmates who make their living (literally!) by acting as agentsof the Z-Loan office and dispatching zombies - Chika Akatsuki, ShitoTachibana, and Michiru Kita - are hot on the trail of an elusivepsychopath known as "The Butterfly." But as if serial killers andzombies weren't enough to worry about, poor Michiru's barely had achace to get used to her new digs, her new life, and...What's this? A newmember!? Chika's friend Shiba joins the teen trio as they solve riddleafter riddle and get ever closer to the madman's lair.