Ryūkotsusei (竜骨精, "Dragon Bone Spirit") was an extremely powerful dragon daiyōkai who terrorized the Plains of Musashi until he was confronted by the Inu no Taishō and sealed to a cliff face in the Valley of Ryūkotsusei. The wounds that Ryūkotsusei inflicted on the Inu no Taishō ultimately led to the latter's death.

Many years later, Ryūkotsusei was reawakened and brought out of dormancy by the hanyō Naraku. Ryūkotsusei had no intention of exacting revenge on Inuyasha, the younger son of the Inu no Taishō, to suit Naraku's purposes, but after destroying Naraku's demon puppet, Ryūkotsusei decided to fight the son of his old enemy to entertain himself. After a very arduous battle, during which Ryūkotsusei was injured many times but never succumbed, Inuyasha finally defeated the dragon with the Bakuryūha and, in defeating Ryūkotsusei, took a major step in the training of his sword, the Tessaiga. (Read more...)