Episode 171

Dragon-Scaled Tessaiga is the fourth episode of InuYasha: The Final Act.

Plot
The episode begins when Sesshōmaru cuts a meidō into the sky to kill a demon. Tōtōsai says this attack is called the Meidō Zangetsuha, which is the true intention of Tenseiga's use. Sesshōmaru has not yet mastered this attack, because his meidō is a half crescent, but should be a full circle.

Back at Tōtōsai's hideout, Inuyasha and Tōtōsai are discussing the demon blade, Dakki. The blade Mujina used was a fake, even though it was made out of one of Ryūjin's scales. You have to have one of Ryūjin's scales, or it is impossible to construct Dakki. Inuyasha wants to find the real Dakki, and defeat it's wielder, to gain it's power in his Tessaiga. Tōtōsai says that if Inuyasha were to lose, Tessaiga would remain a rusty sword forever, because Dakki would absorb all of Tessaiga's demonic energy.

Meanwhile, Tōshū the swordsmith, is finished constructing the real Dakki. Now the demon Ryūjin has come to claim Dakki, the sword Tōshu created for him. Tōshu is hiding, unwilling to give up the finished Dakki. Ryūjin is furious and ready to attack. Inuyasha and friends arrive, and Inuyasha uses his Wind Scar on Ryūjin. Inuyasha sees Tōshū hiding. Inuyasha realizes that his Wind Scar is no use against Ryūjin, because Ryūjin gets his power from his opponent's demonic energy. Kagome, Sango, Miroku, Shippō and Kirara protect Tōshū.

Elsewhere, a giant demon has slaughtered another tribe of wolf demons, and only two young boys, Kai (the eldest) and Shinta (the youngest), remain. Kai is injured by the demon. Byakuya of the Dreams, Naraku's new (and final) incarnation, appears; he is the one controlling the demon. Byakuya spares Kai and Shinta's lives, giving Kai a Shikon Jewel Shard to heal his wounds.

In the meantime, Inuyasha and Ryūjin continue fighting. Inuyasha uses his Wind Scar without effect, Inuyasha is persistent, so Ryūjin uses the demonic energy he has collected from Inuyasha, to attack. This is what Inuyasha wanted, so he waits for the attack, and uses the Backlash Wave, which killed Ryūjin. Tōshū comes and absorbs Ryūjin's demonic energy into Dakki. Now Dakki is complete, Inuyasha and friends are now uneasy about this new side of Tōshu they are beginning to see.

Kōga and friends are traveling when Kai stops them in their tracks. He has to take Kōga's Jewel Shards and bring them to Byakuya by sunset, or Shinta will die. Failing, Kai notices that the sun is beginning to set, frustrating him; Kai runs away, heading back to Byakuya. Kōga follows after Kai, wanting answers as to why he attacked him.

Tōshu challenges Inuyasha, because he wants Tessaiga's demonic energy. Inuyasha and Tōshu engage in battle, Tōshū tells the story of how he created Dakki, which started with him created sharper blades by using ones scavenged from blood-soaked battles fields, and crafting new ones using hatred; when Ryūjin sensed this desire in Tōshū, he approached him and was offered the creation of the powerful sword Dakki. The dragon scales are spreading from Dakki to Tōshu, soon Dakki will completely consume Tōshū.

Kai returns to Byakuya with Kōga behind him; Byakuya says bringing Kōga himself works as well. Kōga uses his Goraishi claws to kill the demon under Byakuya's command. Byakuya retreats, but one of his moths takes Shinta with it, while spreading huge amounts of demonic energy into the sky. Kōga and Kai follow the moth to rescue Shinta. Byakuya knows who will come in search of the demonic energy his moth is sending out.

Elsewhere, Tōshū is now covered in scales, having taken Inuyasha's demonic energy from his attacks. Inuyasha defeats Tōshū, who exploded from Dakki sending all the blows it received into him, and gains Dakki's powers. The Tessaiga can now take the form of dragon scales to absorb demonic energy from Inuyasha's enemies. Inuyasha and friends then notice Ginta and Hakkaku running to catch up with Kōga, in the direction which Kagome senses four Jewel Shards.

Kōga and Kai meet up with Mōryōmaru, who now has Shinta. Kōga's shards are acting up again, as he attacks Mōryōmaru. Mōryōmaru tries to absorb Koga and Kai's Jewel Shards, succeeding in getting Kai's. Inuyasha and friends arrive, and Sango saves Shinta, and Inuyasha saves Koga and Kai. When Mōryōmaru says his armor is invincible, Inuyasha decides to test it and launches the Adamant Barrage; however, once the spears pierce him, Mōryōmaru absorbs them, turning his right arm into an adamant spike. Inuyasha uses the Dragon Scaled Tessaiga on Mōryōmaru, making the wound Sesshōmaru inflicted on the armor open up again. However, Tessaiga begins heating up and Inuyasha is thrown backwards by a backlash of energy. Mōryōmaru releases a cloud of miasma and escapes.

Byakuya appears and says he is impressed by Inuyasha's new attack; if there had been another enemy, Inuyasha would not have faired so well. When questioned if he's the second enemy, Byakuya says that he was only there to observe and leaves. Inuyasha comes to, and wonders what happened to his Tessaiga. The scene ends with a shot of the rusty Tessaiga.

Byakuya rows a boat out to a lake, where he meets with Naraku. Informing him of Inuyasha's new Dragon Scaled Tessaiga. Byakuya asks Naraku if he should have just finished Inuyasha off instead of just observing; he then wonders if they should let Inuyasha use this new power to destroy Mōryōmaru. Naraku wonders which will happen first: Inuyasha being consumed by his own sword, or Mōryōmaru being destroyed by it.

Trivia

 * Byakuya originally appeared when Inuyasha failed at using the Dragon-scaled Tessaiga against a venomous demon, in the manga.