In the United Global Year (UGY) 193, the Earth is under attack from an extraterrestrial enemy, the Radam. The Radam are led by an even deadlier force, known as the Tekkamen.

Surrounding the Earth is the huge man-made orbital ring known as the Space Ring. The Space Ring was constructed well before the arrival of Radam and was the first human structure attacked by them. As the aliens attacked, those that were left either fled or were killed, and the Space Ring was largely abandoned, serving only as a battle ground for Blade and the Tekkamen.

Fighting against Radam and the Tekkamen are the Space Knights. Led by Commander Heinrich Freeman, the Space Knights are a Special Defense Force, and Earth's last hope for defeating the mighty Radam. The Space Knights consist of Noal, the pilot of the Space Knights' ship the Blue Earth, Aki Kisaragi, the Blue Earth Navigator, Milly, Communications Operator, Rebin, computer wiz and mechanic, and Honda, Mechanic and Repairs. The Space Knights have been unsuccessful at repelling the Radam until the arrival of D-Boy (Dangerous Boy - Tekkaman Blade's nickname while amnesiac), a mysterious young man who has the ability to transform into the powerful warrior known as Tekkaman Blade.