In the United Global Year (UGY) 193, the Earth is under attack from an extraterrestrial enemy; the Rahdam. The Rahdam 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 Rahdam and was the first human structure attacked by the 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 Rahdam 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 Rahdam. 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 Rahdam until the arrival of D-Boy, a mysterious young man who has the ability to transform into the powerful warrior known as Tekkaman Blade.

Souchirou Nagi and Bob Makihara are two delinquents who arrive at Toudou Academy with the objective of ruling over the school with their strength. But on their first day, they encountered the Jyuukenbu, a martial arts group of the school. Members of the group, Maya Natsume, her sister Aya, and Masataka Takayanagi easily overpowered Souchirou and Bob. And what's more, due to what was assumed to be their "connections" with the Jyuukenbu, the two were attacked by members of the Enforcement Group, which oversees the martial arts groups of the school. Drawn into the personal conflicts between the Jyuukenbu and the Enforcement Group, Souchirou and Bob have no choice but to join up with Maya Natsume's group and to hone their skills to become even stronger.

Feudal Japan is attacked by beasts called 'Youi'. Ryuudou Yukiatsu, a 'floater' and an employee at a bath house has the power of Ayagami ("The power to find the words behind things") which can be used in fighting against the Youi. That's why the members of a Youi-fighting group Bansha Aratamesho, called the Ayashi, are looking for Yukiatsu - they want him to become an Ayashi as well. Yukiatsu runs into a woman and a son who are chased by a Youi and has to face the past he's been running away from.