The Ultimate Key to Defeating Naraku is the one hundred sixty-fifth episode of the InuYasha anime.


Infant with the Fuyoheki

The Ultimate Key to Defeating Naraku

Inuyasha, Kagome, Miroku and Sango are running down a path, they come across the bodies of several parasite demons. They come to a huge hole in the ground and comment that the local rumors that the mountain had disappeared are true. Inuyasha smells Naraku in the area.

Kagura kills some parasite demons, and sees Kohaku burning a tree of the parasites. She stops to talk to him. Kohaku comments that there is something abnormal about their behavior. Kagura asks Kohaku why Naraku ordered them to kill any parasite demons they came across. Kagura and Kohaku are summoned.

Kanna sits in a cave. Her mirror glows, showing Kikyō's helpers.

Kohaku wonders if the mountain he saw move is the demon from where all the parasites came. Hakudōshi interrupts his musings with comments about Kagura's unreliable behavior. Hakudōshi orders Kohaku to go help Kanna.



Inuyasha and friends come to a mountain that is moving. It is a demon named Gakusanjin and attacks them. When Inuyasha asks if the giant demon is working with Naraku, the demon stops its attack. It tells them how Naraku entered it's body, disturbing it's 200 year sleep with his miasma. Naraku stole a protective stone, the Fuyōheki, from within the demon's body, that allowed him to remain sleeping.

The demon gives them some crystal shards that will help them detect when they are close to Naraku and the Fuyōheki he has stolen.

Kohaku is heading to Kanna when he sees Kikyō's helpers. The Saimyōshō indicate Kohaku should kill them. When he attacks, puppet figures fall to the ground, and Kikyō arrives. While she asks Kohaku why he serves Naraku, the devil she speaks of arrives behind her.

Kagome senses Kohaku's jewel shard. As they approach it, the crystals they received lose their demonic aura, indicating they are approaching Naraku and the stolen gem.

Kikyō holds an arrow nocked, aimed at Naraku, but trembling. She worries that she cannot sense his aura. She shoots the sacred arrow and splits him apart without killing him. Kikyō is trapped within a cage of Naraku's bones. Naraku orders Kohaku to kill Kikyō, as he steps forward to do so, Inuyasha and friends arrive to save Kikyō.

Inuyasha and Kikyō discuss that Naraku must be trying to hide his heart.

Hakudōshi and Kohaku kill a huge demon that consumes human souls. They take the stomach of the demon.

Inuyasha and friends try to follow Naraku and come across corpses of demons scattered. One demon attacks them. When Inuyasha kills it, Miroku notices that something is wrong with the released spirits. They fight a number of demons, and notice the demons are looking more and more human. Inuyasha smells Hakudōshi and they find him gloating over his newest creation. Inuyasha uses his Adamant Barrage. Hakudōshi leaps in front of his creation, and is torn apart - an uncharacteristic move they all notice.

As he retreats, Hakudōshi steals the crystal fragments from Miroku, leaving them no way to detect when they are near the Fuyōheki. Hakudōshi then brings his created demon to the Infant and Kanna. Kanna tells Mōryōmaru that she will put a soul in him, holding the Infant out to the demonic golem.

Characters in Order of Appearance[]


  • Opening Theme — ANGELUS — Best of Inuyasha II
  • Inuyasha’s group finds chrysalis corpses — Shōki — TV OST Vol. 2
  • Kohaku burns tree of chrysalises — The Hidden Well to the Sengoku Era (Kakushi Ido kara Sengoku Jidai e) — TV OST Vol. 1
  • Kohaku realizes that the mountain is likely the host of the chrysalises — Evil Spirits Desiring the Shikon no Tama (Shikon no Tama o Nerau Chimimōryō) — TV OST Vol. 1
  • Mountain demon confirms that Naraku stole his stone — Sign of Unrest (Fuon na Kehai) — TV OST Vol. 1
  • Mountain demon talks about the Fuyōheki’s purpose — The Hidden Well to the Sengoku Era (Kakushi Ido kara Sengoku Jidai e) — TV OST Vol. 1
  • Inuyasha wonders why Naraku needs to hide his demonic aura — Malice (Urami) — TV OST Vol. 3
  • Kikyō confronts Kohaku — Sign of Unrest (Fuon na Kehai) — TV OST Vol. 1
  • Naraku stands behind Kikyō — Naraku’s Treachery (Naraku no Yabō) — TV OST Vol. 2
  • Kikyō says Naraku’s heart is located outside his body — Trap (Wana) — TV OST Vol. 2
  • Hakudōshi sees large demon and human souls — Dead Soul (Shinidama) — TV OST Vol. 1
  • Inuyasha comes across strange demon with human souls — The Disaster at Mount Hakurei (Hakureizan no Ihen) — TV OST Vol. 3
  • Inuyasha’s group fights many demons — Fang Sword, Tessaiga (Kiba no Ken Tessaiga) — TV OST Vol. 1
  • Enter Mōryōmaru — Hakudōshi — TV OST Vol. 3
  • Mōryōmaru can fly — Hell Insects, Saimyōshō (Jigoku Mushi Saimyōshō) — TV OST Vol. 2
  • Hakudōshi gives Mōryōmaru to Kanna — Hakudōshi — TV OST Vol. 3
  • Ending Theme — Brand-New World — Best of Inuyasha II


  • In the manga, Kōga met Mōryōmaru before Inuyasha's group; they arrived second. In the anime Koga does not appear at all.
  • This is the first that Haku and Kon are mentioned in the series. It is mentioned again in Hanyou no Yashahime Season 2.
  • The first time Naraku and Kikyō have met since Mount Hakurei.
  • The Infant and Hakudōshi have begun their plan to betray Naraku.


  • When Hakudōshi sends Kohaku off he says go help Kagura rather than Kanna.
InuYasha Episode Navigation
Preceded by Episode 165
Episode 165
Succeeded by
Episode 164
Possessed by a Parasite: Shippo, Our Worst Enemy!
Episode 166
The Bond Between Them ~ Use the Shikon Jewel Shard! Part 1