After trying to rescue a man on the subway tracks, two teens wake up in a room dominated by a mysterious black sphere that sends them to hunt down and kill aliens hiding on Earth.

Summoned by the black sphere, Kei and Masaru fight against extraterrestrials until Masaru grows tired of fighting and refuses to continue.

Before finding out the Perfect Answer, discover Another Gantz. Aired on Nippon Television network before the theatrical release of Gantz: The Perfect Answer, this film is an alternate perspective version of the first Gantz film from the same writing-directing team of the two-part theatrical film. In addition to condensed scenes from the Gantz film, Another Gantz features a new subplot that follows an investigative journalist not included in the theatrical film. Delving deep into the mystery, Another Gantz offers another piece towards solving the complex puzzle that is the world of Gantz.

After being brutally murdered in a subway station, a teen boy awakens to find himself resurrected by a strange computer named Gantz, and forced to fight a large force of invading aliens in Osaka.