Junki Saiga is a normal high school student with a gift in mathematics. His daily routine is disrupted when his family gets news that his father's remains have been discovered- a noted archaeologist and researcher who had gone missing while exploring a site many years before. Among his remains were notes and artifacts that needed to be identified by the family near a notable triangular mountain in Japan known as "Japan's pyramid", a place suspected by some to be man-made. A meteor containing a strange robotic life-form falls from the sky and begins to cause destruction, putting Junki in danger and causing a mysterious bracelet from his father's research to activate and merge him with an ancient robot buried within the pyramid- a robot the runes describe as Reideen. It is now up to Junki and guardian Reideen to fight against this unknown alien threat from the sky. As the story progresses attacks come from multiple directions: the main aliens, who only want Reideen's power, and will then raze the Earth and move on; a faction within the Vigilance Corps that wishes to discredit and remove Reideen in favor of Human-built remote-controlled mecha; and Roxell, an alien with horns on his head who used a similar giant named Gadion on his homeworld, only to be defeated by the overseer aliens, and his planet destroyed. Some of these enemies want Reideen with or without Junki as its pilot/power source, while others just want Junki/Reideen out of the way. Junki grows continually torn between doing what only he can do, in piloting Reideen against the giant beast machines sent to destroy cities and the landscape, and his enemies' attacks toward him while he does not receive any help from the Vigilance Corps nor his friends.
The giant Reideen appears as a warrior with a hooded head and feather motif. In reality the giant can transform large pieces of itself into other objects to suit his purpose. The following is a list of weapons/equipment wielded by Reideen:
God Arrow - Reideen can materialize a bow and arrow to shoot enemies.
God Wand - A magical staff used to find camouflaged colossal beast machines, or split the God Arrow into multiple blasts at target.
God Sword - Used with Junki's boku sword training to destroy the colossal beast machines.
God Bird - Allows Reideen the ability to fly. A bird head unfolds from Reideen's back, while the arms and legs change to expose ramjet-like engines and streamline the rest of the body. Its bird form can be hardened with a silver coating to pierce through a colossal beast machine's armour. The bird form can fly underwater, but not maneuver well.
God Marine - A vehicle which allows Reideen to move swiftly underwater, as well as fly.
God Voice - A pulse of rings which go in every direction; capable of destroying and capturing targets. Also capable of creating a defensive barrier whilst underwater.
God Wind - An attack which Reideen's front armor glows fiery red; pierces through targets.
Flash Drive - Allows Reideen to move at a lightning quick speed that gives the illusion of teleportation.
God Blade - The ultimate sword, a gigantic blade around the size of the moon itself.
Anime
licensed the series in 2014 and released a subtitled DVD set with the first thirteen episodes on December 16, 2014.
In episode 7 at time 16:30, a scene from the opening sequence of the anime Cromartie High School is recreated with a waist-high view of Junki and the Analysis Section gang strutting in formation down a hallway.
