Grendizer was my true introduction to Anime along with many other Arabic speaking viewers who lived in the Arabic part of the Middle East (I used to live in Egypt), ask any Arab especially those around the age of 30 to make a list of their favorite cartoon shows growing up and it's likely most of them will mention Grendizer. One of the many reasons why Grendizer became such an enormous hit in Arabic speaking countries was because it was the first "Serious" cartoon Arabic viewers have ever seen and something different to other cartoons that were shown at that time like Disney, Looney Toons, Popeye and Tom & Jerry. The giant robot gimmick was an important factor as well.
Grendizer chronicles the tale of a young alien prince named Duke Fleed and his struggle to protect Planet Earth from an alien empire called Vega. Planet Vega has become unstable due to the exploiting of Vegatron, a powerful radioactive ore. Seeking to expand his militaristic empire and find a substitute planet to settle upon, the ruthless King Vega unleashes his armies — composed of flying saucers and giant robotic monsters — and turns first against neighbors such as Fleed, a highly advanced but peaceful world. In a tragically ironic twist, the invaders' blitzkrieg turns against them: the once verdant, idyllic Fleed is turned into a radioactive wasteland.
Using Planet Fleed's highly advanced technology, the Vegan Empire constructed Grendizer, a highly advanced giant robot built in the likeness of the Fleedian God Of War to be used to lead their invasion fleet through other parts of the galaxy, the robot also interfaces with Spazer, a flying saucer that enables the robot to fly. However, the only known survivor of the Fleed royal family, Prince Duke Fleed, manages to steal Grendizer.
Fleeing the Vegan forces, Duke switches course to Earth, making a rough landing in Japan, on the slopes of Mount Fuji. He is befriended by Doctor Umon, a noted scientist who oversees a research laboratory called the Space Science Lab near a small ranch. The kindly Umon takes in the young alien as his son, under the assumed name of Daisuke, and assists him in hiding Grendizer.