Ryūkotsusei

was an extremely powerful dragon daiyōkai who terrorized the Plains of Musashi until he was confronted by Tōga and sealed to a cliff face in the Valley of Ryūkotsusei. The wounds that Ryūkotsusei inflicted on Tōga 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 Tōga, 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.

Sealed by Tōga
200 years before the shattering of the Shikon no Tama, Ryūkotsusei was a feared daiyōkai and created mayhem across the land. Tōga, a powerful dog demon who defended Japan against threats such as Ryūkotsusei, confronted the dragon and engaged him in battle, in order to put an end to his rampage. Ryūkotsusei was a truly terrible foe, however, and not even Tōga could defeat him or put him under seal so easily. The Great Dog Demon had faced many powerful demons in the past and had stopped several invasions by powerful daiyōkai and their armies, but Ryūkotsusei was so singularly powerful that Tōga was fatally wounded before finally using one of his fangs to pierce Ryūkotsusei's thick skin directly above the heart, thus sealing his powers into a state of dormancy. After the battle with Ryūkotsusei, Tōga had been spotted in the land of Kamakura that has been wounded reported to Kirinmaru by Kyūki and Konton, and hurried to the mansion to his wife Izayoi for the birth of his second son on the night of the lunar eclipse until he died as he fought Takemaru.

Revival
200 years later, Ryūkotsusei was visited by Tōga's youngest son, Inuyasha, who was on a mission to strengthen his sword, the Tessaiga, by driving it into Ryūkotsusei's heart and killing him. However, Inuyasha's enemy, Naraku, desired to revive Ryūkotsusei, hoping the powerful demon would be able to destroy his hated foe. Naraku used his miasma to disintegrate the fang of Tōga that kept Ryūkotsusei under seal. Once done, Ryūkotsusei's powers returned and his heart began to beat once more. As he began to stir, a menacing aura began to collect around him, his right hand started to move, darkening the skies and summoning storm clouds. As Ryūkotsusei broke free of the cliff he had been sealed to, Naraku called out to him, telling him that Inuyasha was the son of the one who hurled him into dormancy, encouraging him to avenge himself by destroying Inuyasha.

While the flea Myōga attempted to persuade Inuyasha to flee, Inuyasha expressed his preference for a direct confrontation, since he believed that simply killing Ryūkotsusei while he was dormant to be too cowardly. Ryūkotsusei heard this and asked Inuyasha if he seriously thought that he could defeat him, expressing his amusement at such a notion. Ryūkotsusei lunged forward, crushing the hill Inuyasha had been standing on, proceeding to then fire an energy blast in Inuyasha's direction. While the hanyō dodged the blast, it soon became apparent that Ryūkotsusei's true target was not Inuyasha, but Naraku, who was obliterated. Ryūkotsusei wanted to kill Naraku because he believed him to be an eyesore. However, after destroying him, Ryūkotsusei recognized that what he had hit was just a demon puppet and not the real Naraku, complaining that such a thing hardly constituted a warm-up.

Ryūkotsusei then turned his attention to Inuyasha, expressing his hope that Inuyasha could provide him with more amusement that the demon puppet had. Inuyasha replied that he was more than happy to oblige and attempted to cut Ryūkotsusei by stabbing into the scar left by his father's claw. However, the attack was futile, and Inuyasha was repulsed. Ryūkotsusei taunted Inuyasha, telling him that it was no use since his body was mightier than any armor. He then stated that it was his turn and fired an energy blast at Inuyasha, who barely managed to dodge it in time.

Myōga yet again attempted to persuade Inuyasha to flee, adding that it was his father's battle with Ryūkotsusei and the wounds he was given that ultimately killed him, shocking Inuyasha. Ryūkotsusei was pleased to hear that his old enemy had perished and asked if Inuyasha had come to avenge his father with a ridiculous sword such as the Tessaiga. Inuyasha said he never even met his father, so avenging him was the last thing on his mind. While Myōga scolded Inuyasha for being a "traitorous" son, Ryūkotsusei took advantage of their arguing to slam his tail against Inuyasha, knocking him into a nearby cliff.

Inuyasha charged at Ryūkotsusei, but was met with a continuous barrage of energy blasts which leveled the surrounding landscape. Ryūkotsusei berated Inuyasha for being so weak, claiming that their battle had become more tedious than he expected and that destroying him relieved him of none of the anger he felt towards Inuyasha's father. Inuyasha leapt to attack again, but Ryūkotsusei slammed Inuyasha into a cliff with his claws, telling him again that he would not be able to defeat him with an inferior sword like the Tessaiga. Ryūkotsusei pressed harder into the rock face, demolishing it and leaving Inuyasha to fall into a deep ravine. After Inuyasha dropped the Tessaiga and plummeted to the bottom of the ravine, Ryūkotsusei fired off yet another energy blast, that left Inuyasha badly injured.

However, as Ryūkotsusei closed in, Inuyasha's aura began to change, as his demon blood took over his body without the protection of the Tessaiga. This transformation confused Ryūkotsusei at first, but he realized that Inuyasha's demon blood had awakened and accepted it, since it would prove more of a challenge. In this state, Inuyasha was much stronger and even capable of piercing Ryūkotsusei's skin, causing him a minor injury. Ryūkotsusei told Inuyasha not to get ahead of himself and fired an energy blast, leaving only a crater behind. Ryūkotsusei soon realized that he had missed and was unable to dodge Inuyasha's next attack, which sent him crashing into a cliff. This was Inuyasha's original intent, as he wanted to retrieve the Tessaiga from under Ryūkotsusei, who had slithered over top of it. As Inuyasha went to claim it, Ryūkotsusei became angry at Inuyasha's arrogance at thinking that he could defeat him, and fired an energy blast at him; however, Inuyasha was saved by the barrier of the Tessaiga's sheath. Ryūkotsusei declared angrily that Inuyasha would not be able to stop his blast a second time, which according to Tōtōsai was the truth. However, Inuyasha was saved yet again, this time by the monk Miroku using his Kazaana to alter the course of Ryūkotsusei's blast slightly.

Death
Inuyasha finally reclaimed his sword, reversing his transformation. Ryūkotsusei told Inuyasha that he was very weak, pointing out that he couldn't even hold up his sword. Inuyasha replied that he had his reasons for needing the Tessaiga to defeat him. Ryūkotsusei laughed at him and told him that this time he wouldn't hold back. As he attacked Inuyasha once again, Inuyasha dodged the blast and stabbed his sword into Ryūkotsusei's heart, the Tessaiga having become lighter for him after his earlier declaration. Although it caused him a great deal of pain, Ryūkotsusei was not affected in any way, and indignantly told Inuyasha that he would pay for wielding his sword against him. Ryūkotsusei's resiliency surprised even Inuyasha and his friends, as he proceeded to fire a string of energy blasts at Inuyasha. The hanyō attempted to strike back, but was slammed into a cliff once again by Ryūkotsusei's tail. Ryūkotsusei laughed at Inuyasha, telling him that he had warned him that his sword was useless.

Ryūkotsusei fired another energy blast at Inuyasha, but it was overcome by the Kaze no Kizu, which plummeted into Ryūkotsusei and sent him reeling back. Although Inuyasha realized he could now invoke the Wind Scar at will, Ryūkotsusei quickly recovered and as he rose, asked Inuyasha if that was the best he could do. Inuyasha was unnerved that not even the Wind Scar phased Ryūkotsusei. The dragon proclaimed that "play time" was over, and that this time he would destroy Inuyasha, as he amassed an immense demonic aura and fired one last, colossal energy blast. Inuyasha couldn't avoid it since it was so gigantic, so he decided to cut through it with the Wind Scar, creating the Bakuryūha, which successfully took control of Ryūkotsusei's demonic energy and reversed the flow back towards him. Ryūkotsusei watched in horror as whirlpools of his own demonic energy sliced his body to pieces. Ryūkotsusei's head was destroyed, and he lamented the destruction of his invincible, rock-hard body before his face was finally obliterated by the Backlash Wave. The remaining pieces of his body crumbled to dust and were blown away with the wind.

Sesshōmaru, later visited the Valley of Ryūkotsusei along with Jaken, A-Un, and Rin and he was certain Inuyasha killed him although he didn't know how, much to Jaken's surprise.

Personality
As befitting his tremendous power and size, Ryūkotsusei is an extremely self-assured demon who does not think he can be defeated, viewing any attempts to thwart him as amusing diversions. Because of his size and thick, armor-like skin, of which he is exceedingly proud, Ryūkotsusei believes himself to be invincible and as such he has no sense of danger or fear. This immense confidence in his own power and resiliency allows him to lead a very carefree existence. He is constantly looking for a challenge to entertain himself, but constantly views opponents of lesser size and power to be worthless. He knows nothing besides battle and destruction and according to Tōtōsai, if he were to rise again the entire Plains of Musashi would be razed to a field of ashes, implying that, despite his obvious intelligence, he has no other motivation than to destroy things for his own amusement, so much so that it would be inevitable that he would destroy the surrounding area.

Ryūkotsusei is also completely merciless and did not hesitate to obliterate Naraku, the very demon who had released him from his seal. He even went so far as to plow straight past Inuyasha to attack Naraku, ignoring Inuyasha and going to attack an opponent who was farther away. He did so because he considered Naraku an "eye-sore", possibly because he could tell that Naraku was merely a half-demon, but more probably because he was enraged by Naraku's hubris in thinking that Ryūkotsusei could be used as a tool to destroy Inuyasha. Ryūkotsusei, despite his own massive pride, is extremely intolerant of any arrogance others possess in thinking that he could be defeated or overcome in anyway, or in Naraku's case, to think that he could use Ryūkotsusei for his own purposes. Ryūkotsusei attacked and destroyed Naraku's demon puppet to prove how futile such efforts were. When Inuyasha actually managed to wound Ryūkotsusei, rather than be worried (since the attack was ultimately ineffective), Ryūkotsusei was enraged that Inuyasha even dared to think to wield his sword against him.

Despite his ruthless streak, Ryūkotsusei toyed with Inuyasha and did not use his full power in order to prolong the fight and make it more entertaining. However, once Inuyasha had used his most powerful attack, which failed to even scratch Ryūkotsusei, he grew bored and prepared to use his full power to destroy Inuyasha, which, if not for the Bakuryūha, surely would have killed the hanyō. Unlike most demons, especially powerful daiyōkai, Ryūkotsusei never makes an issue out of Inuyasha being a half-demon, nor indeed does he even mention it. This is highly irregular, since powerful demons view half-demons as weak and pathetic. Considering that Ryūkotsusei views everyone this way, it is possible he simply does not see any difference in this perceived weakness, or that he is so powerful that he stands above the petty squabbles between demons and half-demons.

Physical description
Ryūkotsusei was an extremely large dragon daiyōkai with a long serpentine body, two four-fingered arms, and purple skin. When sealed, Ryūkotsusei's skin is of a greenish-brown hue, but turns back to purple when he is revived. His head was typical of a dragon, except for the fact that he had a face embedded in his forehead, which was reminiscent of a mask used in traditional Japanese theatre. This mask was white, with vertical purple markings coming up from his eyes and either side of his jaw, as well as two stripes jutting down from the top of his head and two curved lines on either side of his face. The mask had glowing red eyes, thin, black eyebrows, colored blue lips, and sharp, fang-like teeth. Ryūkotsusei used this mask to communicate with others, as his normal dragon body did not have the capacity for speech. Very long, gray hair emerged from the top of the mask and continued down Ryūkotsusei's back, all the way down towards the tip of his tail. Two, flat, triangular horns, similar in appearance to ears jutted out from along Ryūkotsusei's browline, in between which lay the mask. Like his mask, Ryūkotsusei had glowing red eyes, but instead of simple dot-like pupils, had thin, slit pupils. He had sharp fangs, capable of crushing boulders and two very prominent fangs in the front that jutted down from his jaw and could be seen when his mouth was closed. He had whiskers on either side of his jaw that were the same color as his skin. Ryūkotsusei's hide was extremely tough and ridged, with a prominent scar in his chest near his heart, from where Tōga had pierced him with his fang. After he is destroyed, pieces of Ryūkotsusei's body fall like shards of pottery, owing to the fact that his body really is "rock-hard." Ryūkotsusei is one of the few daiyōkai, other than Gōra, who do not appear to have a humanoid appearance that they can disguise themselves in.

Attacks

 * Energy Bullet: This is Ryūkotsusei's primary form of attack, and it is an extremely dangerous blast of demonic energy fired from Ryūkotsusei's dragon mouth. At first, he requires some time to charge it before attacking, but once he has fired one, he is able to fire many consecutive blasts in quick succession, a truly devastating attack that can level the entire surrounding landscape. This attack is so powerful, that even the barrier created by the Tessaiga's sheath could only withstand it once; according to Tōtōsai, a second attack would have destroyed it. Not even Miroku's Kazaana was strong enough to pull in the energy blast once it had been fired, only managing to slightly alter its course, barely missing Inuyasha.
 * Super Energy Bullet: A variation of his standard energy bullet, when Ryūkotsusei strengthens his aura and gathers enough yōki, he is able to create an enormous sphere of energy that dwarfs Inuyasha. This attack is so powerful that Inuyasha's friends are forced to flee the scene for fear that they will be caught up in the blast. This is Ryūkotsusei's most powerful attack and arguably one of the most powerful attacks of any of Inuyasha's foes. Ultimately, it was the energy from this attack which Inuyasha used in tandem with the Backlash Wave to defeat Ryūkotsusei.

Powers

 * Enhanced Defense: Arguably Ryūkotsusei's most distinctive trait in battle, his thick hide provides him with a near invincible defense, that renders most attacks useless. Neither the Tessaiga nor even the Kaze no Kizu were able to have any effect on him. Tōga was only able to pierce his hide once, and even then was unable to deal him a finishing blow, having to resort to put Ryūkotsusei under seal instead. Inuyasha's full demon form was capable of piercing Ryūkotsusei's hide with his claws and knocking him down with his raw strength, but even these attacks did the dragon little actual harm. Ultimately it required combining a Kaze no Kizu with Ryūkotsusei's own ultimate attack to deal him any real harm.
 * Superhuman Resiliency: Even when his thick skin does not shield him from an attack, Ryūkotsusei is still able to cope with the damage and it does not do him any lasting harm. Inuyasha attempted to stab him directly in the heart in order to defeat him, yet even this was not enough to kill him. Ryūkotsusei cannot die from any attack unless his body is shattered or cut into pieces, otherwise he will continue to rise and fight.
 * Superhuman Strength: Due to his immense size, Ryūkotsusei possesses unrivaled strength and is able to crush mountains with his bare hands and smash boulders with his jaws alone. His size itself is a formidable advantage, as he destroyed an entire cliff side just by landing on it after being sent back by Inuyasha. He often uses his tail to slam opponents into cliff faces or to simply crush them. A simple swish was enough to level an entire hill that Inuyasha had been standing on.

Manga vs. Anime

 * In the manga, Ryūkotsusei is never shown to have destroyed Naraku's demon puppet, this is seen only in the anime.
 * In the anime, Ryūkotsusei's fight with Inuyasha is expanded far beyond how it is depicted in the manga.

Trivia

 * Ryūkotsusei appears in the second InuYasha ending, "Fukai Mori", where Sesshōmaru visits the valley of Ryūkotsusei and reflects on his father's legacy. Perhaps as a tribute to this, after Ryūkotsusei is destroyed, Sesshōmaru visits the valley shortly before the third and final invasion of the Panther Tribe to survey the area after hearing that Inuyasha had defeated Ryūkotsusei.
 * The events of Tōga's battle with Ryūkotsusei are further explained in Swords of an Honorable Ruler. The film states that directly after the battle between Ryūkotsusei and Tōga, Tōga was forced into saving Inuyasha and his mother before he had recovered from the injuries inflicted by Ryūkotsusei, thus contributing to his death.
 * Ryūkotsusei is the first opponent of Inuyasha to be defeated by the Bakuryūha. He will typically only use the move on truly powerful opponents who cannot be overcome by the Wind Scar. The next opponent he uses it on will be Hyōga in InuYasha the Movie: Affections Touching Across Time, which chronologically takes place shortly after Inuyasha's battle with Ryūkotsusei. In the anime and manga, Tsubaki is the next foe to be defeated by the Backlash Wave. Ryūkotsusei often appears in flashbacks when the Backlash Wave is used.
 * Ryūkotsusei is also the first in a long line of his father's former enemies that he must defeat, including Menōmaru and Shishinki.
 * Ryūkotsusei is arguably indirectly responsible for the the creation of the Rainbow Pearls, since it was Tōga's death, largely caused by the wounds Ryūkotsusei inflected upon, that drove Zero to wish away her emotions with the Shikon Jewel, which created the pearls.
 * His seiyū, Kazuhiko Inoue, also voiced several characters from Rumiko Takahashi's previous shows. They include Mikado Sanzenin from Ranma ½ and Tsubame Ozuno from Urusei Yatsura.

Media appearances
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Manga

 * Chapter 188
 * Chapter 189
 * Chapter 190
 * Chapter 191
 * Chapter 192

Anime
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 * Episode 53
 * Episode 54
 * Episode 55
 * Episode 75
 * Episode 157