Three computer-savvy kids, Naoto, Yuka and Ippei created their own videogame superhero, but then discover it possessed by an inter-dimensional police officer, Gridman. Pursuing an evil program called Kahn Digifer, he merges with Naoto and fights Kahn Digifer's digitized monsters (created by social misfit Takeshi) in order to prevent the computerized demon from wreaking havoc on the Human World.

Ippei and Naoto's teacher encourages them to do better in their studies.

Terragaia runs wild in the computer system of the Waterworks Bureau; Gridman falls for a trap and gets captured; an Assist Weapon is dispatched to save Gridman.

Takeshi creates a monster that hacks a shopping mall's cash register system.

A criminal known as Phantom Thief Marty burglarizes a dozen homes; Ippei's treasured soccer ball is stolen.

Naoto and Ippei spend some time at the local sports center's indoor pool.