One day, breaking the peaceful silence of Ayaka City, the giant kaiju, Gurugioboru appears! The giant monster starts to rampage through the city, spitting a heat ray from his mouth. Two brothers, Katsumi and Isami try and escape, but suddenly they are both cornered! Just then, the Rube Gyro and Rube Crystals appear before them! The two brothers will use these items to transform into the giants of light known as Ultraman!