Ryūkotsusei

was a dragon daiyōkai who fought with Inu no Taishō long before the main storyline. He never was able to fully kill Ryūkotsusei but managed to seal him into a dormant sleep with one of his claws. Soon after this battle however, Inu no Taishō succumbed to his injuries and died.

History
After Tessaiga was destroyed by Goshinki, Inuyasha had to get it reforged using one of his own fangs. Unfortunately for Inuyasha though, Tessaiga became much heavier than before and became harder for him to wield. After seeking an explanation from Tōtōsai and Myōga, he goes off stubbornly, to kill Ryūkotsusei. Myōga explained to Inuyasha that he only had to strike Ryūkotsusei in the heart and he would've surpassed his father. However, Inuyasha disagreed with this method saying that it wasn't his style. Unfortunately for Inuyasha, Naraku had removed Inu no Taishō's claw, reawakening Ryūkotsusei, in hopes that he would be able to destroy Inuyasha.

Reawakening
With the claw removed, Ryūkotsusei awoke to see Inuyasha. They immediately engaged into a fight with Ryūkotsusei on the offensive. Unbeknownst to Inuyasha, Ryūkotsusei was aiming for Naraku's demon puppet before truly turning his attention to him. He learns that Inu no Taishō had died from the very battle that had sealed him and that Inuyasha was his son. Ryūkotsusei constantly looked down at Inuyasha calling him a 'little boy' and ridiculing Tessaiga on its effectiveness against him.

Death
Inuyasha managed to kill Ryūkotsusei by using the Bakuryuha (without realizing it) on one of Ryūkotsusei's Thunder Bullets which tore the demon into pieces. From Ryūkotsusei's death, Inuyasha has surpassed his father. (Also somehow Inuyasha managed to easily defeat Ryūkotsusei using the Bakuryūha even though Inuyasha's father died due to a similiar battle). Sesshōmaru would later follow in these same footsteps, upon forming the Bakusaiga.

Appearance
Ryūkotsusei has the appearance of a typical dragon but with a mask on his head. This mask is Ryūkotsusei's real face as it does the talking and directs the body while the dragon's mouth shoots out powerful energy blasts. Both the mask and the dragon have red eyes. Its long body is covered in thick armored hide which is near impenetrable as Inuyasha quickly realizes. He has two fairly short arms, despite this, he was able to slam Inuyasha up against the cliffside without struggle. Along with his large intimidating body, his demonic aura can easily disintegrate rocks without even having the dragon come in contact with it. Unlike other powerful demons, Ryūkotsusei does not appear to have a humanoid appearance.

Abilities

 * Enhanced Strength: Ryūkotsusei was able to dominate over Inuyasha for the first half of the battle, only to momentarily overwhelmed by his demonic transformation. His full power was not shown in the series, but it was enough for one of the strongest characters in the series, the Inu no Taishō, to be unable to defeat him and had to seal him away, and is the ultimate reason for his death; suggesting he was very formidable.


 * Enhanced Defense: Ryūkotsusei has an incredible armored hide that is nearly impenetrable, even striking the scar Inu no Taishō's claw left in it had no effect. However, when Inuyasha transformed, he was able to inflict wounds on Ryūkotsusei with his claws alone. After Inuyasha repossessed Tessaiga, he was able to stab Ryūkotsusei in the heart and use the Kaze no Kizu on him; however Ryūkotsusei did not die despite these attacks.


 * Thunder Attack Bullet: These large, powerful, pure white energy spheres are launched out of Ryūkotsusei's mouth and can be fired numerous times consecutively. In the anime, it was so powerful that when; Miroku used his Kazaana on one of these blasts, he was only able to change its course slightly. Tessaiga's sheathe was able to protect Inuyasha from one of these attacks.

Trivia

 * Ryūkotsusei appears in the second ending; Fukai Mori.


 * The events of Inu no Taishō's battle with Ryūkotsusei are further explained in Swords of an Honorable Ruler. The film states that after the battle Inu no Taishō was forced into another to save Inuyasha and his mother before he had recovered from the injuries inflicted by Ryūkotsusei, thus contributing to his death.