|Nickname||The Monster's Monster|
|Fighting Style||Nada Shinkage-Ryu|
|Family||Seiko Miyazawa (Twin-Brother)|
Yumiko Miyazawa (Older Sister)
Son-O (Older Brother)
Kichi Miyazawa (Nephew)
Marcio Naito (Adoptive Son)
Various unnamed children
One of the main antagonists of the series, Kiryu Miyazawa (宮沢鬼龍, Miyazawa Kiryū) is considered as the incarnation of the devil by anyone who has met him. He is more of an anti-hero type as he constantly pushes Kibo to surpass his limits.
Unlike his brother, Kiryu is wicked and completely ruthless. He is also an intellectual that quotes philosophers, appreciates art, and read many books even when hospitalized. But this is only another facet of his ruthless nature, because Kiryu values mental and physical strength above all else.
Kiryu looks almost exactly like his brother Seiko, since they are identical twins. The only exception being that Kiryu has slicked back hair, a scar across his face and he doesn't wear glasses.
- Superhuman Endurance: Kiryu has been able to fight with severe physical injuries, including gouged eyes, crushed throat and broken arm.
- Kiryu possesses the physical condition in his legs called the Dragon's Foot (Japanese:
龍腿蹴, Doragon Shūto).
- In the side story Tankōbon "Oton", it is revealed that Kiryu fathered a child with the daughter of the United States President.
- Kiryu can play the piano.
- He managed to train a kangaroo, the animal manage to win a fight in a boxing match.