Nine and Twelve, two seemingly normal kids, but the product of a secret and inhumane government experiment, are wreaking havoc on Tokyo under the terrorist name "Sphinx." Instead of massacring random people, the two plant strategic bombs around the city and launch video puzzles online, challenging the police to solve them before the explosion to expose the government's subterfuge. Their plans are thwarted by Kenjirou Shibazaki, a veteran and mistreated detective who quickly grasps the psychological game behind the attacks. The situation is further complicated by the arrival of Lisa, a nerdy high school student who accidentally gets caught in the middle of the action, and Five, a government agent and old acquaintance of the two kids, determined to turn the challenge into a no-holds-barred personal feud.