When they were in fourth grade, best friends Hiroshi Tamiya, Riku Kaneda, and Katsuya "Dafu" Tabuse created a secret hideout in an abandoned factory. They called it the "Hikari Club," and it became a fun place where the boys could break away from their bleak lives and focus on playing chess and practice shooting targets with their slingshots. However, when Hiroyuki Tsunekawa stumbles into the hideout, the club has no idea what is in store for them.

Hiroyuki becomes obsessed with the concept of world domination, and begins to steer the Hikari Club towards creating an intelligent robot. As the club's membership begins to grow and the robot's construction progresses, Hiroyuki's influence grows as well. With the original purpose of the club long forgotten, Tamiya wonders if he can ever get his childhood friends back.